The Temporal Displacement Experiment
The Door into SummerTwitchell's uncertain device turns Dan's desire to inspect the past into a dangerous experiment whose apparent randomness is ultimately contained within a self-consistent history.
increasing
Bearing strength in each event
decreasing
A Classified Discovery

A Classified Discovery
An unexpected effect
Hubert Twitchell's gravitational experiments produce temporal displacement, first demonstrated with coins and later with animals. The objects return at uncertain times, and the device cannot reveal which temporal direction it will select.
A military fantasy
Officials imagine using the effect to move troops across time, but its unpredictable direction and high power requirements make it useless as a reliable weapon. The secret classification survives even though the system is not operationally practical.
The Missing Human Test

The Missing Human Test
Vincent disappears
Leonard Vincent undergoes a major displacement and does not return within Twitchell's lifetime. The scientist cannot know whether the colleague arrived in the past or the future.
A moral limit
The disappearance makes Twitchell reluctant to expose another person to the device. His restraint contrasts with the military and scientific desire to treat people as experimental material.
A Risk Explained

A Risk Explained
No reliable direction
Chuck tells Dan that the machine cannot identify which mass will move forward and which will move backward. Even a successful displacement may put a person in the wrong era, inside an obstacle, or far from any possibility of return.
Return is not guaranteed
Dan would also need money, equipment, and a way to reach the temporal apparatus again. The explanation makes the journey plainly hazardous, but Dan's unanswered questions outweigh the warning.
The Deliberate Provocation

The Deliberate Provocation
A rehearsal requested
Dan persuades Twitchell to set up a simulated human displacement, claiming he wants to understand the apparatus. He then declares that the demonstration is a hoax and challenges the scientist to prove otherwise.
A real displacement
Twitchell, stung by the insult, pushes the switch. Dan vanishes from the laboratory and finds himself in 1970, where the supposed rehearsal has become the decisive event of his life.
The Loop Closes

The Loop Closes
Events already recorded
Dan realizes that his work in 1970 accounts for patents he encountered in 2001. His trip to the past does not create a separate history; it supplies the actions that have always belonged to the one he remembers.
The apparent choice
He concludes that the timeline excludes actions that would prevent the conditions producing them. Time travel can occur, but only within a history whose connections and feedback keep it coherent.
During the early work at Boulder
During Twitchell's earlier experiments
Spring 2001, over beers with Chuck
May 2001, at Thornton Memorial Laboratory
After 1970 and the second awakening in 2001