California, 1987. Bumblebee is ambushed by Sector 7 and escapes, only to be attacked by Decepticon Blitzwing, who rips out his vocal processors and leaves him to die before being destroyed by Agent Burns (John Cena). Bumblebee is later found and repaired by local teenager Charlie Watson (Hailee Steinfeld), and befriends her and her friends, but does not remember who he is.
Meanwhile, S7 Agent Powell (John Ortiz) meets Decepticons Dropkick and Shatter, who claim Bumblebee is a dangerous criminal from their homeworld and convince Powell to help them capture Bumblebee. The Decepticons are winning the war and hunting Autobots across the galaxy. Powell, Burns, Dropkick and Shatter pursue Bumblebee to Charlie’s hometown and capture Charlie to lure Bumblebee into a trap.
Bumblebee regains his memories and realizes his mission is to defend Earth from the Decepticons. He confronts and defeats Dropkick and Shatter. Burns, realizing that Bumblebee is not the enemy, allows him to escape. Bumblebee bids farewell to Charlie and leaves.
Optimus Prime appears in a hologram and Megatron appears frozen at S7’s base of operations at Hoover Dam. Barricade also reportedly appears. Dropkick and Shatter are triple-changers and lovers. Bumblebee’s relationship with Charlie is purely platonic, and she becomes involved with her friend Memo (Jorge Lendeborg Jr.). Cybertron is featured in flashbacks.
The movie was originally a prequel to Michael Bay’s series, particularly 2007’s TRANSFORMERS. In the original ending, Bumblebee scanned the ’77 Camaro mode, in which he would later meet Sam Witwicky (Shia LaBeouf). After positive feedback, however, sizeable reshoots were ordered to change it into a reboot. In the new ending, Bumblebee reportedly retains his Beetle mode, regains his voice and is sent on a new mission. Optimus Prime also comes to Earth, setting up his own movie, and more Cybertron flashbacks were added to feature more Autobots and Decepticons that could appear in the sequels.