Run, Fatboy, Run

Dennis Doyle stands at the threshold of his wedding, gripped by anxiety and uncertainty about marrying his pregnant fiancée, Libby. This moment of doubt leads him to question not just his readiness for marriage but the entire direction of his life.

Overwhelmed by his fears, Dennis makes a rash decision to flee the wedding, leaving behind a mixture of regret and unresolved emotions. His hasty exit sets the stage for the conflicts that follow in his life and relationships.

Fast forward five years, Dennis discovers that Libby has moved on with the charming Whit, who has managed to win her heart with his confidence. This revelation stirs a fierce desire in Dennis to reclaim the love he abandoned.

Motivated by the impending Nike River Marathon in London, Dennis sees this as an opportunity to not only challenge himself but also to win back Libby. He recruits his eccentric friends Gordon and Mr. Ghoshdastidar to aid in his marathon training.

During Libby's birthday party, Whit seizes the moment to propose, deepening Dennis's feeling of despair and illustrating the stakes of his mission to win Libby back. This proposal serves as a major turning point for Dennis's determination.

As Dennis wrestles with the decision to drop out of the marathon, a heartfelt moment with his son, Jake, inspires him to face his fears. Witnessing Jake's struggles with rejection brings clarity and determination back to Dennis's life.

Dennis recommits to the marathon, entering into a fierce competition with Whit. The race is filled with excitement, as both men push beyond their limits, showcasing their determination to win the affection of Libby.

During the race, tensions escalate as Whit attempts to trip Dennis, resulting in a painful injury. This incident not only affects Dennis physically but also highlights the lengths to which Whit will go to undermine him.

As medical help arrives at the scene, Libby rushes to assist Dennis only to find Whit feigning injury and trying to shift blame onto him. The situation becomes a powerful demonstration of character and deceit between the two men.

Despite the pain from his injury, Dennis continues to push forward, rallying with the support of his loyal friends. This determination reflects his growth as he battles not just for victory, but for his family and self-worth.

As the marathon progresses, footage is shown at Whit’s house revealing Dennis's struggles with Whit, exposing Whit's previous claims as lies. This moment catalyzes a shift in Libby’s perception and strengthens her resolve.

As the truth becomes clear to Libby, she reaches a breaking point and places her engagement ring on the table, deciding to leave with Jake. This pivotal moment signifies her reclaiming agency in her life and relationships.

Despite his fatigue and injuries, Dennis receives encouragement from Libby and Jake as he nears the finish line. Their support revitalizes him, allowing him to sprint towards the end and collapse into their arms as they celebrate.

In a hopeful moment, Dennis visits Libby's home to invite Jake on an outing and hints at important discussions with Libby. This tentative step forward suggests the possibility of rekindling their relationship.

The film concludes with a humorous scene featuring Gordon as he entertains two elegantly dressed women with extravagant tales of his experiences aboard his luxurious yacht. Gordon's antics provide a lighthearted cap to the story.