Mother: Eve McBain
Sibling: Michael McBain
Cousin: Shannon McBain
Significant Romantic Relationships: Caitlin Fitzgerald, Natalie Vega, Evangeline Williamson

John McBain grew up in Atlantic City, the son of a cop and a lounge singer. When his father died at an early age, John was forced to help raise his younger brother, Michael, while his mother worked to support them. Inspired by his father, John began a career in law enforcement, eventually joining the FBI. He fell in love with a woman named Caitlin, and the two planned to marry. At the time, John was investigating a serial killer in New Jersey, and publicly taunted the killer at a press conference. Shortly afterward, the serial killer (Stephen Haver) murdered Caitlin out of revenge.

John threw himself into his work. He came to Llanview in 2003 as part of an undercover operation to arrest Flynn Laurence, a criminal who had his hand in many illegal operations. John infiltrated Flynn's organization, and at Flynn's orders, traveled to Llanview to recruit Natalie Vega for an upcoming tournament. John convinced Natalie to compete in a tournament in Las Vegas that Flynn was overseeing. Flynn ordered John to have Natalie throw the game. Natalie refused, and Flynn soon kidnapped her. John revealed his true identity as an FBI agent to Natalie's husband, Cristian and the two worked together to rescue Natalie. However, Cristian was seemingly killed in the process.

John returned to Llanview, where he was placed on the investigative team for the Music Box murders, which seemed to be the work of a serial killer. John grew close with the Llanview PD staff, and developed a friendship with Natalie, despite her initial resentment over his role in Cristian's death. John was shocked to discover that the Music Box Killer was Stephen Haver, a man that he had hired as a consultant on the case. He soon learned that Stephen was the same man responsible for killing Caitlin years earlier. When Stephen was arrested for the serial murders he found another way to torment John. He planned his own death, and framed John for his murder. John was arrested, but with the help of lawyer Evangeline Williamson and cop friend Antonio Vega he was proven innocent. John thought he was free of Stephen forever, but soon after he had a major health episode. It turned out Haver had poisoned prescription pills John took periodically for a past injury, and nearly killed John in the process. Natalie nursed John back to health and the two grew closer. It soon became clear their feelings for each other went beyond friendship.

Kathryn Fitzgerald, Caitlin's sister, came to town after being threatened by the Santi crime family. John and Kathryn had previously worked together in the FBI and her visit to Llanview caused even more friction for Natalie and John. Natalie misinterpreted their closeness, and became involved with Paul Cramer, who Kathryn claimed had Santi ties. Together, John and Kathryn confronted Paul on his involvement with the Santi's, and had him testify against the thugs that were after her. Kathryn was now safe to leave Llanview, but before she left she confessed to John that she always had feelings for him. John decided to maintain a professional and platonic relationship with Kathryn, and did not pursue a romance. Natalie's involvement with Paul, however, escalated when she followed him out to Atlantic City. While there Natalie realized she still had strong feelings for John, who had followed the couple to Atlantic City. Natalie decided to end things with Paul to explore her feelings for John. Natalie and John nearly consummated their relationship, but Natalie put a stop to things when it became clear John was not over the death of Caitlin.

When Paul Cramer went missing and blood was found in his Atlantic City hotel room, Natalie was a prime suspect. Kathryn came back to Llanview to investigate Paul's disappearance, and questioned Natalie. John defended Natalie, and refused to believe she would have a hand in killing Paul. John was right, as Paul soon showed up alive and well. Natalie and Paul picked things up where they left off and John concentrated on the Santi investigation.

The Santi case turned personal for John when Kathryn Fitzgerald's body turned up in Evangeline Williamson's office. Shortly after, a client of Evangeline's was murdered, and it turned out both victims had ties to the Santi mob. John and Evangeline made a visit to the widow of her client one night, and ended up trapped in her wine cellar. After a couple bottles of wine and some conversation one thing lead to another, and John and Evangeline slept together. Both brushed it off as a one time thing, but their strong attraction developed into something more. When Evangeline broke up with RJ, he reacted jealously by hiring some thugs to beat John up. John paid RJ back when he busted an art heist RJ had planned. RJ had enlisted the help of Paul and Rex Balsom, who had gotten Natalie to help them. John arrested all three, but decided to let Natalie go. Eventually, Natalie came to her senses and broke up with Paul, and John did his best to assure Paul left her alone. When Paul was murdered, all evidence pointed to Natalie as the killer, and John was forced to investigate. Natalie confided in him that Paul attacked her on the night of his murder, but she was not responsible for his death. Later an eyewitness and further evidence cleared Natalie of the murder.

John's relationship with Evangeline became strained when both found themselves on opposite sides in the Tico Santi murder investigation. John believed Antonio was the top suspect, while Evangeline agreed to be Antonio's attorney. Despite their different positions, the two agreed to try not to let their personal lives interfere with their professional ones, and they grew closer.

John was stunned when Cristian returned to town very much alive. John quickly noticed a tortured and violent side to Cristian, and warned Natalie he could be dangerous. Slowly he became convinced that Cristian was not Cristian at all, and shared his suspicions with Natalie. Disbelieving, Natalie agreed to a DNA test in order to prove John wrong. Before the results came in, Cristian confessed to killing Tico and admitted to Natalie that he was an imposter. Natalie was devastated. Cristian was sent to prison, but not before John received the DNA results---which revealed that the imposter really was an amnesiac Cristian. To spare Natalie the pain of a husband imprisoned for life, Cristian asked John to keep the ruse that he was an imposter, so Natalie could move on. John wrestled with the decision, and agreed, letting Natalie believe her husband was dead. Despite this turmoil, John and Evangeline have reaffirmed their commitment to each other, even though John's feelings for Natalie remain an ambiguous and unresolved area in his life.