In 2008, Toronto musicians Matt and Jay form "Nirvanna the Band" in the hopes of landing a single show at the Rivoli. Seventeen years pass, and the duo still has not secured a gig, their schemes repeatedly failing and straining their friendship.
Matt proposes a bold publicity stunt, the Seventh Inning Skydive, aiming to plunge from the CN Tower into the SkyDome during a Blue Jays game. The plan blows up when the SkyDome roof shuts mid-dive, intensifying Jay's frustration with Matt's reckless ideas. Jay quietly books an open mic slot in Ottawa while Matt grows convinced they can win over Rivoli by posing as time travelers. He outfits their RV with fake time-travel gear inspired by Back to the Future, but a spilled bottle of Orbitz sabotages the setup.
The next morning, Jay tries to head to Ottawa in the RV, only to learn that Matt is still inside, and the pair are unexpectedly hurled back to 2008 when the machine springs to life. Realizing Orbitz made the machine work, they scramble to obtain another bottle from their younger selves’ apartment. They narrowly avoid discovery, and an exchange between the younger Jay and the older Matt makes the older Jay rethink leaving the band. The older Matt learns of the solo plan and, in response, convinces the 2008 versions not to play the Rivoli.
Returning to 2025, Jay has become a wildly successful musician, while Matt drifts into a role as a drummer in a Jay McCarrol cover band. At a concert, Matt confronts Jay about the time machine, but Jay denies any knowledge of it. Afterward, Jay sneaks away and smashes the last Orbitz bottle. In Jay's celebrity world, he finds life hollow and lonely, and his attempt to forge friendships with a new band ends in tragedy when he accidentally shoots and kills one of them, turning him into a fugitive. He returns to Matt, still insisting he is the alternate version, proposing to fix the timeline—but his real aim is to undo the scandal.
With Orbitz unavailable, Matt recalls the night of the failed skydiving plan: a lightning strike hit the CN Tower. They attempt to power the time circuits by running a cable from the tower to a power box at a street intersection. As authorities close in on Jay, the cable loosens from the tower, forcing Matt to reconnect it. The end is tense: the cable is too short to reach the power box. As Matt tries to plug it in, news arrives that Jay has murdered someone. He completes the circuit by sacrificing his own body to power the machine.
Witnessing the sacrifice, Jay returns to 2008 and tweaks Matt's earlier message to encourage their younger selves to play the Rivoli. In the present, Matt suggests launching the skydiving stunt again, unaware of the earlier timeline's consequences. Jay proposes starting the plan earlier to sidestep the complications.
