Starscream shows off the massive Energon deposit that the Decepticons have located. After Megatron reminds his subordinate who's boss, he shows off what he's found — Dark Energon, the blood of Unicron, which Starscream claims is said to have the power to resurrect the dead. Megatron inquires if Starscream is willing to volunteer to try it out, but it turns out they still have Cliffjumper's corpse handy.
At Autobot HQ, Optimus Prime tells the kids that the Autobots will have to protect them, as the Decepticons will likely be interested in the Autobots' new allies. A proximity alert lets the Autobots know that Agent Fowler, their liaison with the US government, is paying them a visit. Fowler is not happy with the Autobots' antics during the recent freeway chase, but Bulkhead points out that no humans were hurt. After Prime's assurances that the Autobots will take care of things, Fowler leaves.
Megatron uses the Dark Energon on Cliffjumper, who revives as a snarling, savage, zombie-like beast and immediately attacks a couple of Decepticon soldiers. The thing that was once Cliffjumper then turns on Megatron, who slices him in two and announces that the Dark Energon is the key to a vast, indestructible army.
Ratchet reports that he's detected Cliffjumper's signal, and the chance that Cliffjumper's alive is too much for the Autobots to resist. Leaving the kids with Ratchet, they take the Ground Bridge out. Ratchet explains the Ground Bridge to the amazed kids and threatens to send them to Tokyo.
Meanwhile, the rest of the Autobots arrive in the Energon mine and start fighting Vehicons, the Decepticon drones. Starscream alerts Megatron, who feels he needs more time to prepare to face Optimus and orders the ship made ready for departure. He also orders Starscream to blow up the mine. As the battle rages, Arcee spots Cliffjumper. The other Autobots cover her, and she reaches her fellow Autobot, or what's left of him, only to discover what the Decepticons have done. Starscream stops by to drop off a bomb before making a rapid exit. The Autobots race through the mine ahead of the explosion, back to their entry point, as Optimus radios Ratchet to order the opening of the Ground Bridge.
After the team arrives back at base, Arcee tells the others what she saw. She becomes dizzy, and Ratchet scans her and finds contamination (Dark Energon) on her wrist. While Arcee goes and gets cleaned up, the kids explain to Optimus that they really need to get home, or their relatives will send the cops out looking for them. Prime assigns Bulkhead to take Miko home, Bumblebee to take care of Raf, and Arcee to watch over Jack. Arcee and Jack arrive home shortly before Jack's mother arrives in her car. Jack's mom is less than impressed that Jack appears to have bought a motorcycle, but Jack's talk brings her around. The next morning, despite Jack's protests that it's a Saturday, Arcee insists that they need to get to HQ.
On the Decepticon ship, Megatron is skeptical that Optimus perished in the destruction of the Energon mine. Starscream is concerned that Megatron is being affected by too much exposure to the Dark Energon, but Megatron responds by taking a sliver of the substance and plunging it into his own Spark.
Ratchet's analysis of the Dark Energon sample he retrieved from Arcee is incomplete due to his lack of the necessary technology. As he moves the sample to another part of the lab, some of it drips on the manipulator arm Bulkhead broke earlier. Unseen by Ratchet, the arm twitches into life, turning into a one-eyed, spider-like creature.
- Came Back Wrong: Cliffjumper.
- Mr. Exposition: Optimus has some explaining to do when the kids show up at base.
- No Indoor Voice: Agent Fowler.
Miko: Robots...who get dizzy?
Raf: Robots...with emotions.
Jack: Robots...who can die.