Bob is visited by a familiar-looking stranger while writing his thesis on time travel. The stranger is "Joe " and claims to be from the future and wants Bob to go through the black gate.
Another stranger comes through the gate that looks like Joe and does not wnt Bob to go through. Bob is eventually punched into the gate.
Bob meets Diktor who is a king from 30,000 years in the future. Diktor explains that aliens built the gate and that humans are now obedient slaves. Diktor tells Bob to bring a man he sees back through the gate.
Bob unknowingly reenacts the first scene, this time as the man "Joe." The man after "Joe" claims that Diktor is only trying to entangle and confuse him, but Bob again returns to Diktor's world.
Bob collects the items on the list Diktor requests (which are all useful items for a man making himself king). He then sets the gate back 10 years earlier to try to rise to power before Diktor can.
While adjusting the gate to look back, Bob then realizes that HE is Diktor and all the other events before were just earlier versions of him. He then sends back the earliest Bob to ensure his own future.