Destiny's recent intergalactic battle has left her with serious damage. The scientific team briefs Young about her feeble structure as well as the minimum of supplies they now have. Everyone faces the hard truth that this could be the end of the line - everyone except Eli. Against Rush's protestations, Eli tells Young that, while Ginn was alive, the two of them worked out the calculations for dialing Earth. It's only possible while Destiny is repowering in a star - an event which is close upon them, and which Rush warns against for its plethora of unseen dangers.
Still, it seems to be the crew's only chance for survival, so Young must proceed. After the finest minds on Earth have reviewed Eli's calculations, everyone prepares to go home, but as Rush readies to address the masses, making a final plea for volunteers to stay and complete Destiny's mission to find the intelligence at the foundation of the cosmos, he and Young are called away - a subspace communication was picked up from none other than Rush! The confusion only heightens when the second Rush, in his spare shuttle, is brought aboard and tells a story of the wormhole to Earth turning unstable just after Telford, the forward guard, passed through.
He states that everyone died in the attempt, but he managed to stay behind and find a shuttle, then, in a freak temporal event, was sent back in time and is able to warn the "young" Destiny not to make the attempt. Young and Telford doubt the veracity of his tale, but they're interrupted when Brody alerts them to the presence of the second Destiny - also sent back in time - and the need to board her in order to gather any supplies she may have that could ensure their survival for at least a little while longer. Telford leads a team, including both Rushes, onto the ship and they gather as many electrical supplies and foodstuffs as they can.
On their way back to the young Destiny, the Rushes spot a device that could double their weapons capability. The older Rush attempts to work it free, but while the younger Rush searches for the proper weapons, Telford has a heart to heart with the temporal Rush, demanding the truth. They come to blows and Rush shoves Telford into the weapons device, sending a volt of energy through Telford's body that ends his life. Rush, shocked, flees the scene just before his double, accompanied by Scott, arrives. Young orders both men to return to the ship as time is running out, but Rush seeks out - and finds - his other self at the very chair that made Franklin transcend to another plane. The younger Rush demands the truth about the attempt to dial Earth, but the older Rush persists with his story, pressing the younger instead for help: If he's going to sit in the chair and access the wisdom of the Ancients, he needs someone to start the program.
The task done, the younger Rush hurries back to his Destiny. Finding an explanation for how Telford died is pressing, especially since his alternate, who successfully traveled to Earth, wants to use the stones to visit Destiny to find out why the others didn't follow.