Forming an aliiance with Megatron against Unicron, Optimus gave the Key to Vector Sigma to Jack. Optimus hoped that Jack would keep it safe for him. Jack promised Optimus that he won't let him down. When Optimus lost his memories, Jack had an idea of letting the Decepticons build their space bridge. When the team secured the space bridge, Jack and Arcee traveled on Cybertron to restore Optimus' memories.
After some time, they uncovered Vector Sigma underneath Kaon. While Arcee was dealing with an insecticon, Jack traveled and uncovered Vector Sigma's room. Jack put the key on Vector sigma's power cell and it downloaded the data into the card. Jack tried to fend off the Scraplets that were eating away the machine. Suddenly the insecticon, that Arcee fought, made its way to Jack's location. Jack threw one scraplet at the insecticon, while the others followed. They devoured the insecticon and fell off Vector Sigma's platform. Jack and Arcee traveled back to the space bridge, only to find out that it was a trap. Arcee transformed and jumped at Megatron, who was waiting for them but was stopped by Orion Pax. Jack downloaded Optimus' memories into "Orion" and Optimus was reverted back to his original form.