The Autobots and Decepticons are engaged in battle near a strange cave surrounded by a Stone Henge-like structure. Starscream, Rumble, Ravage and Ramjet duck for cover inside the cave and are magically transported to England of 543 AD. Low on Energy, they meet up with Sir Wagond of Blackthorne, a king who wishes to overthrow his enemy, Sir Aikling the Red. Aikling's daughter, Nimue, overhears the allegiance and attempts to bring the information back to her father. Ravage pursues her and she bumps into Spike, who is accompanied by Warpath and Hoist.
Warpath, Hoist and Spike follow Nimue back to her father's kingdom and find out that Aikling and Wagond's dispute is over a broken fence. Wagond shows up and demands Aikling meet his new champion knight in a joust; Rumble riding atop Ramjet like a steed. Aikling reluctantly agrees and armors-up. Warpath agrees to act as his steed and Aikling defeats Rumble in the joust. Starscream is fed-up with the foolishness and kidnaps Nimue, demanding Aikling's kingdom in return.
Wagond returns with the Decepticons to his castle only to have his gold be taken by Starscream and used to make wire for an electric dynamo. Once energized, Starscream creates charcoal while he sends Ramjet and Ravage to gather rock-salt and sulfur and gives Rumble the ugly task of acquiring potassium nitrate (mass quantities of bird crap). Starscream mixes the ingredients and creates gun powder to use against the on-coming forces of Aikling the Red and the low-on-energy Autobots. Meanwhile, Wagond admits to Nimue that he never wanted to start a war and the pair fall in love.
Aikling and the Autobots storm Wagond's castle but are over-powered by the refreshed Decepticons and their gun-powder explosives. Merlin soon shows up and summons lightning from the sky which re-energizes the Autobots. Re-powered, the Autobots trash the Decepticons. They drag them back to the time gate only to find it guarded by a fearsome dragon. Merlin gives them some of his "Dragon's Bane", which turns out to be gun powder. Warpath fires the gun powder into the dragon's fiery breath and it explodes, sending the dragon away. The Transformers and Spike return to the present and back into battle with the Decepticons. Starscream, um, "tackle-hugs" Megatron in his enthusiasm, ruining Megatron's shot at Hoist and Warpath. Starscream wonders why Megatron isn't happy to see him as Megatron screams in anger.