Marilyn and Peter had been friends, good friends, towards the end of her life. Marilyn moved to Brentwood to be near Peter and sought his advice and shoulder whenever things weren’t going well for her.

Marilyn, taken with JFK on their first meeting Peter arranged, asked Peter to give him her number, which he did. This move sparked an affair between the two that would see Marilyn attempt to commit suicide on several occasions, and see her dive into a deep depression over a relationship she wasn’t emotionally able to handle.

Peter, as a good friend, offered his home to Monroe and JFK, so they could conduct there affair – the same courtesy he offered to RFK and Monroe later on. Peter would pass and receive messages between Marilyn and the Kennedys without question.

One thing Peter didn’t count on was Marilyn falling in love with JFK, that caused problems for himself and the Kennedys. When JFK wanted to end the relationship with Marilyn, Peter was there to console her, even though he thought the Kennedys were being cruel, he wasn’t willing to lash out against their decisions as he knew the dangers involved.

Marilyn often felt betrayed by Peter and indeed some of his Rat Pack buddies, as they frequently chose their loyalty to the Kennedys over her and her welfare. Peter was always the bearer of bad news on behalf of the Kennedys to everybody it seems, as he not only informed Sinatra of the change of plans for Kennedy’s Palm Springs visit, but he also was the one that had to convince Marilyn that the affairs with the Kennedy brothers should end. When she wouldn’t listen and was threatening to tell the public, he got harsh with her and told her that she was just another of JFK's women and to forget it. When she still wouldn't listen, Frank and Giancana were the ones that had to step up and present pictures of Marilyn taken at the Cal-Neva Lodge, in compromising positions and the threat to reveal them to the media if she didn’t keep quiet. Peter was the one that delivered the news to Marilyn that her affair with RFK was over, and that he had seen the photographs in question and was disgusted.

Marilyn felt betrayed by Peter and indeed the Kennedys and Sinatra – all people she thought were her friends. It was hard for Marilyn to accept the fact that JFK hadn’t been in love with her, and wasn’t going to leave Jackie for her. RFK wasn’t going to leave his wife either, to pursue a future with Marilyn. All her hopes of going to the White House and being First Lady were shattered – all dreams she based on conversations, comments and hints she received from the Kennedy brothers concerning their relationships with her.

On the day of her death, Peter’s 3rd last act of betrayal towards Monroe was when he accompanied RFK to her home to inform her that the affair was over, and help to search for bugs and any evidence that would link Marilyn to the brothers. Hoping to confirm his place in Marilyn’s good books again, Peter invited her to a party he was holding that night, but she declined the invitation. Peter’s 2nd last act of betrayal was that he rang her on several occasion during the night to check on her, and sensed something was wrong but was reluctant to involve himself because of his Kennedy connection, an act that contributed to her death.

Before following his instinct of going to Marilyn’s home to check on her, he sought advice of Milt Ebbins, and other people, while she was in her last hours. The last act of betrayal and a final measure of Peter’s loyalty to the Kennedys was when he went over to her home after she had passed away and cleaned up. He removed any evidence, tapes, diaries etc that could link her to the Kennedys.

Peter spent the rest of his life haunted by the knowledge that a large portion of the blame for her death was his. Not only had he been instrumental in creating the situation that sent her over the edge, but when she called out for help in her final hours, he vacillated for hours as her life slipped away but in the end paid for it, as a number of producers in Hollywood wouldn’t use him in their films either because of Sinatra’s blacklisting, or because they were disgusted by the situation surrounding Monroe’s death. Peter also suffered all the blame from the Kennedy family concerning her death, which strained and lead to the end of his association with them.