Steve and Dan are ducking a giant guard, who is pursuing a previously unseen little person. This individual, Thorg, teleports them away with a device he identifies as a STM ("space time manipulator"). He and his partner Berna are time travellers and researchers. Thorg shows off by showing the two men scenes from Earth, and even the very day they departed from Los Angeles before crashing.
When the giant's dog grabs Thorg, Steve grabs the STM and uses it to send him and Dan back in time to avert the whole crash. Thorg and Berna go back to maintain temporal continuity, and a chase ensues. The two travellers can't send the men back - they now have to "go forward" the way they originally did. They shrink Dan and Steve to force them to cooperate, but the men escape.
Left with no choice, they go back and this time the travelers use a pill to enlarge them to normal size...and scramble their memories. Before the drugs kick in, Dan and Steve try to persuade the passengers that the ship will crash. Failing to do so, they try sabotage but forget what they're doing. They relive the crash without changing anything other then a few distant memories and a brief note that Steve left himself.