Rock star Aldous Snow faces a harsh reality after the release of his new album and its lead single, "African Child," which receives dismal reviews, even being labeled by NME as "the worst thing to happen to Africa since the apartheid." Following this professional failure, his girlfriend Jackie Q (played by Rose Byrne) takes their son Naples away from him, leading Aldous into a downward spiral of excessive drinking and drug use.
On the other side of the spectrum, we have Aaron Green (portrayed by Jonah Hill), an ambitious college graduate working as a talent scout at Pinnacle Records in Los Angeles. Balancing his demanding job and the struggles of a relationship with his girlfriend Daphne (Elisabeth Moss), who is consumed by her internship, Aaron finds himself in a tough spot as Pinnacle Records grapples with financial losses. When the company’s head, Sergio Roma (Sean "Diddy" Combs), seeks fresh ideas, Aaron proposes bringing Aldous to perform at the Greek Theatre in celebration of an iconic anniversary show.
As he embarks on a journey to retrieve Aldous from London, Aaron’s life begins to unravel. An emotional farewell with Daphne quickly turns sour when their discussion about moving to Seattle escalates into a fight, leaving Aaron feeling uncertain about their relationship. Once he tracks down Aldous, chaos ensues as they make their way through the city, missing flights and indulging in a wild night of debauchery, where Aaron’s phone inadvertently shows Daphne unflattering glimpses of his antics.
Despite the chaos, the duo finally arrives in New York for Aldous' highly-anticipated return performance. Under pressure from Sergio to keep Aldous sober, Aaron sacrifices his own sobriety to ensure Aldous stays on track. As the performance approaches, Aldous struggles to remember the lyrics to "African Child," leading to a moment of panic for Aaron as he attempts to salvage the situation. What follows is a spontaneous performance of one of Aldous' classics, "The Clap," igniting excitement among the crowd.
However, Aldous's personal demons begin to surface, compelling him to push Aaron further into morally questionable situations, including smuggling drugs. Along the way, Aaron discovers that Aldous is merely masking a profound loneliness stemming from separation from his son and a lack of love from his own father. Despite attempts to encourage Aldous to confront his issues by seeking reconciliation with Jackie and his father, the road trip quickly spirals into more disarray, involving mishaps and a disastrous encounter with drugs that leaves Aaron believing he is having a heart attack.
Their misadventures reach a climactic point when Aldous inadvertently creates a scene that puts them in danger, but amid the chaos, Aaron learns vital lessons about himself, his relationships, and the burden of responsibility. The seconds before the performance invite a moment of introspection as Aldous is reassured by Aaron that he is loved and waited for by thousands of fans.
Arriving at the Greek Theatre, Aldous is ready to perform despite his injuries, while Aaron, feeling disillusioned, decides to leave his job in favor of embracing a healthier path in his personal life. In the end, after months apart, Aaron finds peace in Seattle, where Aldous, having embraced sobriety, enjoys renewed success, fueled by their unforgettable escapade, culminating in Aaron's own triumphant story lined with life lessons and genuine connections.
