Barney Panofsky is navigating life alongside his best friend Boogie in the beautiful city of Rome. In a whirlwind of emotions, he marries the troubled and unfaithful Clara Charnofsky after she claims to be carrying his child. However, the joyous anticipation turns to heartache when Barney discovers that the stillborn child is not his, leading him to demand a separation. Overwhelmed by grief, Clara takes her own life, prompting a devastated Barney to return to his hometown of Montreal.
Upon his return, Barney crosses paths with a woman who eventually becomes his second wife — the daughter of a wealthy Jewish family. Their opulent wedding introduces Barney to Miriam Grant, and he is instantly captivated by her beauty. Although he confesses his feelings to her that very night, she turns him down, leaving him yearning for what could have been.
Despite being married, Barney's affections for Miriam remain persistent as he sends her flowers and gifts. Meanwhile, Boogie, seeking a detox retreat, comes to stay at Barney's serene lake house. Unbeknownst to him, he stumbles upon his friend in bed with his wife, which initially gives Barney a reason to divorce her and pursue Miriam. Yet, as tensions rise between the two friends, Barney’s integrity is put to the test during a drunken confrontation. > "Why are you snorkeling?!" he yells, before accidentally causing chaos and passing out.
When Barney regains consciousness, he finds Boogie missing. A detective tries to extract a confession from him, but Barney's father, Izzy, defends him. Clinging to the hope that Boogie has simply fled, Barney's search continues.
After finalizing his divorce, Barney musters the courage to ask Miriam out, traveling to New York City where they finally embark on a romantic relationship. They marry and welcome two children while Barney finds success in producing a television series. After Izzy dies unexpectedly in a brothel, Barney is left feeling a mix of laughter and tears, affectionately dubbing his father a "King." With happiness in their lives, the couple enjoys their time until a trip to the lake house introduces Barney to Blair, a radio professional who rekindles Miriam's old passions.
As the years pass, their son Michael leaves home, and Miriam expresses her desire to return to the workforce. Barney attempts to dissuade her, but she is determined, finding support from Blair in securing a job at a radio station. However, tensions rise when Barney misses Miriam’s first live interview, opting instead to indulge in drinking and hockey. Despite Miriam's unwavering loyalty, Barney's reckless ways push her to take a weeklong visit to Michael, where, in her absence, he succumbs to temptation and has an affair with a former actress.
Barney confesses his infidelity, leading to their divorce. Shortly after, Miriam finds love again with Blair. As Barney's mental state begins to deteriorate — marked by lapses in memory — he is haunted by the tragic discovery of Boogie's body nearby, apparently perishing in a skydiving mishap. When Miriam offers to meet for lunch, a poignant moment arises. After wandering off to the bathroom, she finds that Barney has forgotten they are divorced, treating her as if the years had not passed.
Barney's condition continues to decline until his eventual passing. During a somber day at the lake house, his children notice a "water bomber" plane dumping water — a stark reminder of the urban legends surrounding Boogie's fate. In the heart-wrenching final scene, Miriam visits Barney's grave, placing roses on a tombstone inscribed with both their names, encapsulating a complex tale of love, loss, and enduring memories.
