Wilson Joel's life takes a tragic turn when his wife Liza unexpectedly dies by suicide. In his deep sorrow, he discovers a sealed letter that he believes is her suicide note. Overwhelmed by grief and unable to confront the contents of the letter, Wilson becomes increasingly addicted to inhaling gasoline fumes, a dangerous habit he picks up in his desperate attempt to cope with the loss. His mother-in-law, Mary Ann, tries her hardest to support him during this challenging time while also grappling with her own sorrow.
To cover up his addiction from his coworker, Maura, Wilson fabricates a story about the petrol smell in his house being due to his hobby of flying remote-controlled planes. In an effort to connect with him, Maura brings her brother-in-law, Denny, an RC enthusiast, to visit Wilson. As Denny prepares to meet him, Wilson visits a hobby shop and discovers he was misled; model planes actually run on glow fuel rather than gasoline.
When Maura eventually expresses her feelings for him, Wilson reacts by fleeing the situation, embarking on a road trip from Indiana to New Orleans as he becomes more disoriented while huffing. His journey leads him to an RC competition in Slidell, Louisiana, where he unwittingly causes chaos by swimming in the lake during the event. Denny, witnessing this, explains to the frustrated competitors that Wilson has just suffered the loss of his wife.
Following a return journey with Denny, Wilson is urged to read Liza's letter. However, he is horrified at the thought of doing so in front of anyone. Once home, he discovers that his house has been robbed, and the emotional turmoil leads him to a breakdown as he becomes increasingly entrenched in his addiction. This culminates in losing a job opportunity when a client catches him huffing glow fuel with neighborhood kids.
In a desperate act, Wilson breaks into Mary Ann's home in search of memories of Liza. There, he finds her belongings and finally comes across Liza's letter, now in Mary Ann's possession. With great resolve, Wilson returns home and opens the letter. In a moment of revelation, he learns that Liza's last wish was for him to find someone else to love while cherishing her memory. After reading her heartfelt closing words, "Love, Liza," Wilson strikes a match and incinerates the letter, inadvertently igniting the gas fumes in his home. He quickly sheds his burning clothes, but the flames grow, forcing him to escape into traffic, clad only in his underwear, as he faces the devastation around him.
