Dr. Lucas Jones told Dr. Griffin Munro, his friend from medical school, about an opening at General Hospital. To Lucas' surprise, Griffin took the job and replaced Patrick Drake. Lucas had no idea that Griffin harbored two secrets: he was a priest, and he was Duke Lavery's son, conceived before Duke had met Anna Devane.

In time, Griffin met Anna and told her about his connection to Duke and his desire to get to know his father through the woman that Duke had loved. Anna was stunned when Griffin showed her a letter from his mother. The letter explained that Griffin's mother had conceived Griffin during a brief affair before Duke had moved to the United States and met Anna. Griffin's mother had kept the secret because by the time she'd tracked down Duke to tell him about the baby, he'd already been in love and happy with Anna.

A DNA test confirmed Griffin's story, and Anna welcomed him into her life and opened up about his father, including his connection to the mob and how he'd been killed in mob hit just after Anna and Duke had decided to run away and start a new life together.

Griffin urged Anna to forgive in order to find peace, but Anna was unable to forgive Carlos because he had no remorse for killing Duke. Griffin advised Anna that forgiveness was the greatest gift from God.

Meanwhile, Griffin met Maxie Jones and discovered that she was engaged to someone from his past -- Nathan West. However, Nathan had no idea who Griffin was because Nathan had been in a drunken rage when he'd caught his ex-wife, Claudette, in bed with her lover and shot him as he'd fled. Griffin was ashamed of the role he'd played in the destruction of Nathan's first marriage and kept his secret from Nathan.

Griffin and Anna's faith was tested when it was revealed that Duke's killer, Carlos Rivera, was alive. However, Carlos had been mortally wounded and was rushed to the hospital, where Griffin was forced to administer last rites. Anna was livid that Griffin had neglected to mention that he was a priest and would give Carlos last rites, but Griffin's faith demanded that he help someone in need -- including his father's murderer.

Eventually, Anna forgave Griffin for his deception, but he refused to explain why he'd taken a leave of absence from the church. After Anna left town to visit with her daughter, Griffin was shocked when a familiar woman showed up at the hospital with an injured knee. It was Nathan's ex-wife, Claudette. Griffin knew that she was trouble and was certain that she had an agenda for being in town. He accused her of loving the thrill of having slept with a priest and the danger of being caught by her husband. Claudette denied it, but Griffin didn't believe her.

Claudette realized that Griffin had never told Nathan that he'd been the man that Nathan had shot.

Griffin confirmed that Julian was in good health and was able to attend his arraignment, however, Julian suddenly went into distress, and his heart monitor flatlined. Griffin called a code blue. Later, Griffin advised Julian he'd suffered a cardiac episode, and Griffin had no idea why.

At the nurse's station, Griffin questioned why Finn had Julian's file. Finn advised that all department heads were required to sign off on a patient when the patient suffered a mystery illness. Griffin and Finn gave Julian a quick exam, and Griffin felt the arrhythmia might have been the result of a panic attack.

When Griffin entered an examination room, he and Claudette were shocked to see each other. Claudette immediately hugged him, but Griffin gently pushed her away and asked her why she was in Port Charles. She said she'd applied for a job at Crimson. Claudette confessed she'd never intended to fall in love with a priest, but Griffin had been the only person who'd understood her. Griffin reminded her that their illicit affair had tortured him and kept him up at night. He'd been mentally and spiritually ill and took full responsibility for his past.

Later Griffin entered the conference room for a staff meeting. Claudette was there and said she'd taken a job with the hospital. Griffin was determined to tell Nathan that he'd been the one Nathan had shot. Claudette begged him not to and said the information would send Nathan into a rage. Griffin knew Claudette loved to toy with people's emotions. Claudette said everything had changed when she'd found him. She wanted him to admit he loved her. Griffin gave in to temptation and kissed her but regretted it immediately.

In the locker room, after his shower, Griffin searched in his bag for something. Claudette flirtatiously held up a pair of his boxers. They were both startled when the power went out. Griffin told Claudette that darkness followed her wherever she went and asked for his boxers. He asked Claudette to leave, but she refused because they had unfinished business to discuss. Claudette wanted him back in her life and believed Griffin still loved her. Griffin placed her hand on his scar and told her all he felt was the pain of being shot.

Griffin assured Claudette he still had a calling and accused her of being a selfish person who lied and only cared about her own happiness. Griffin wanted to know why she'd gone looking for Nathan. Claudette became evasive.

Andre called Griffin to examine Elizabeth after her fall down the stairs. He told Elizabeth that she'd suffered a mild brain concussion, a contusion to her spleen, and a few broken bones, but if all went well, she'd go home in the morning.

When Griffin returned to the locker room, he found a syringe in the trash can. He removed it with a paper towel and later told Monica about the syringe and that he'd dropped it off at the lab for testing. When Griffin received the results, he advised Monica that the syringe he'd found in the trash had been filled with derisifol. Griffin suspected the killer had staged the power outage to cover his tracks.

At the nurses' station, Finn overheard Franco ask Griffin for an update on Elizabeth. Griffin informed him that Elizabeth had hemorrhaged more than they'd anticipated and that they'd run out of her rare blood type. Griffin explained that the power outage had cut off the electricity to the coolers where blood was stored, resulting in a very limited blood supply. Griffin told Franco that Elizabeth's best chances were to receive a blood donation from a family member who was close by.

Griffin bumped into Maxie at the park. He apologized to Maxie for not identifying himself, as it had given Claudette an opening to inflict more damage on Maxie and Nathan. Maxie suggested he seduce Claudette to find out what her agenda was. Griffin was shocked and refused, fearing it would give Claudette false hope. Maxie said that Griffin was not the pious and penitent man he pretended to be -- he was just a man.

At the Floating Rib, Griffin thanked Sonny for meeting with him. Griffin revealed he'd spoken to Anna several time but hadn't wanted to trouble her with his concerns about Julian's trial. In spite of the fact that it was an airtight case against Julian, Griffin worried that Julian might not face justice. Sonny said that Alexis had worn a wire, and the authorities had the recording of Julian taking responsibility for ordering the hits on Duke and Carlos. Sonny added that he and Alexis would testify at the trial.

Griffin expressed his concern because Alexis had been erratic lately. Sonny explained that Alexis had been drinking more than usual because her confidence was at an all-time low, and Alexis was reeling about being wrong about Julian's love for her. Sonny also told Griffin that when Julian had returned to Port Charles, he'd used Danny as a shield by refusing to bank bone marrow when Sonny had threated to kill Julian. Sonny told Griffin how Duke had been able to contain Julian without killing him.

Griffin couldn't understand how he could trust a woman who'd covered up Duke's murder and only stepped forward when Julian had tried to frame her. Sonny assured Griffin that Alexis had paid for her mistakes because she'd been humiliated, lost her job, and almost died at the hands of a husband who had claimed to love her. Sonny encouraged Griffin to honor Duke by giving Alexis the benefit of the doubt. Sonny knew that was what Duke would have done. Sonny assured Griffin that Julian would get justice, but Griffin didn't want Sonny to take matters into his own hands.

Griffin then spotted Robert Scorpio and asked Sonny to introduce him to Robert. Robert informed Griffin and Sonny that he'd spoken to Anna, and she'd extended her stay with Robin and Emma. Anna wanted to make sure that Griffin wouldn't think she'd abandoned him.

Griffin demanded to know what Claudette's agenda was and why she had inserted herself into Maxie and Nathan's lives. She wanted Griffin to tell her she still had a chance with him. Griffin insisted they couldn't be together because they'd caused too much pain, and he wanted to move on. He asked Claudette to honor his request, leave Maxie and Nathan alone, and leave town.

In the park, Griffin heard Scott on a phone call telling a reporter that Julian would be acquitted. Griffin was stunned, and when Scott finished his call, Griffin questioned Scott about the trial and identified himself as Duke Lavery's son. Scott said he worked for Julian and told Griffin to speak to Alexis, Sonny, or Paul.

Griffin went to the Quartermaines' to help Michael make arrangements for Sabrina's memorial. Griffin told Michael the arrangements were set, and it was time for Michael to grieve. Griffin urged Michael to let go of his anger because it would eventually turn against him.

Claudette demanded that Griffin go to her suite because she had important information for him. When he arrived, she said they might have a daughter together and that Nathan would be there shortly with the paternity results. When Nathan and Maxie arrived, Nathan revealed that the paternity test had revealed that Nathan was the father. Later, Griffin questioned the timing of Claudette's confession. Griffin told Maxie he'd talk to Claudette later, and they could compare notes with what Claudette had told Nathan.

Later, when it was discovered that Nathan was not Charlotte's father, Claudette told Griffin that he really was the father. Griffin took Charlotte to Anna's because he needed help. He also shared that Valentin had been released from prison and was in Port Charles. He didn't want to leave Charlotte unattended. Anna thought it was best until they knew that Valentin wouldn't pose a threat to Charlotte.

Later, Anna told Griffin that DNA confirmed that Griffin wasn't Charlotte's father. He noted that Charlotte had been happy to see Valentin and had jumped into his arms. Griffin couldn't believe that Claudette had lied again about Charlotte's paternity. Valentin produced Charlotte's birth certificate that listed Valentin as the father. Valentin cut his finger, wiped the blood with a napkin, and handed it to Anna to run another DNA test. Valentin left Charlotte in Griffin's care until the DNA results returned.

Griffin and Anna arrived at Nina's office and were shocked to see Valentin playing with Charlotte. Griffin received a call and learned that the DNA test revealed that Valentin was Charlotte's father. Valentin wanted to take Charlotte home, but Anna intervened. Later, Griffin admitted it had been painful to discover he wasn't Charlotte's father, but Anna advised him to fight and show that he was the better parent for Charlotte. Anna promised to do everything she could to make sure Charlotte stayed with Griffin.

At Kelly's, Valentin advised Griffin to get used to the idea that Valentin was Charlotte's father. After Valentin left, Griffin told Anna he was apprehensive and didn't think the judge would rule in his favor.

In court Anna provided Judge Rawlins with documentation about Valentin that showed him to be a murderer with a sketchy past. Judge Rawlins asked if Charlotte knew Valentin, and Charlotte called him papa. Charlotte hugged Valentin. Judge Rawlins ruled in favor of Valentin. Charlotte also admitted that she'd called Griffin daddy because her mother had told her to. Griffin said goodbye to Charlotte and promised he'd always be there for her. Anna promised Griffin she would keep digging.

In February 2017, Valentin arrived at the hospital, carrying Anna and yelling for help. Anna had passed out at Wyndemere. After a battery of tests, Anna was diagnosed with polycythemia vera, a rare blood cancer. Griffin assured Anna that with regular phlebotomy appointments and medications, her illness could be managed. However, he stressed that she would have to make some changes to her lifestyle because she would always run the risk of bleeding out if she were ever seriously injured.

Griffin worked closely with Hamilton Finn on the case, but Griffin became concerned about his colleague when Finn began to ask for prescriptions for pain medicine. Griffin decided to talk to Hayden about her boyfriend's odd behavior. Griffin feared that Finn had been dealing with drug withdrawal because Finn had taken a highly addictive drug for years to treat a deadly disease.

Griffin's friendship with Sonny continued to deepen. When Sonny asked Griffin to officiate Sonny and Carly's vow renewal, Griffin saw through the ploy and urged Sonny to be honest with Carly about Sonny's infidelity. Sonny reluctantly agreed that Griffin was right.

In March 2017, Griffin encountered a ghost from the past when he saw Olivia Jerome in the hospital. Olivia had survived a shooting decades earlier and had lived in hiding until she'd learned of Duke's murder. Determined to be united with the love of her life, Olivia kidnapped Griffin, strapped him to a table, and attempted to use an Eastern ritual to raise the dead. Griffin seized the opportunity to pretend to be his father when he realized that Olivia had also abducted Anna. Griffin and Anna worked together to foil Olivia's plans.

In May 2017, Monica Quartermaine asked Griffin to supervise Finn as Finn completed a drug recovery program. Griffin's concerns for Finn mounted when Finn failed his drug tests. Finn insisted he was clean, but Griffin was skeptical. Hayden implored Griffin to help catch the person trying to undermine Finn, so Griffin agreed. Everything pointed to Brad as the culprit, but unbeknownst to everyone, the saboteur was Liesl Obrecht.