The Forest of Time is a Speculative Fiction novella by Michael Flynn first published in 1987 and anthologized several times since. It's set in Pennsylvania in an alternate timeline in which the American states failed to form a union after the Revolution, and have been engaged in small-scale wars over territory ever since.
Because of this hostile state of affairs, when military scout Rudi Knecht stumbles across a stranger in the woods, Hernando Kelly, he assumes him to be a spy and captures him. Kelly, however, has a crazy story about how the mysterious device he's wearing lets him hop between alternate timelines. He started in our own world, but since making his first jump he's been unable to get home, probably because the act of jumping itself is subtly changing the timelines as he goes.
Meanwhile, the various military officers in Knecht's base have different agendas for Kelly. The Hexmajor (military psychiatrist) assumes that Kelly is delusional and tries to hypnotize him into believing that he always lived in this timeline. Kommandant Vonderberge, who really wanted to be a scientist, thinks that the story is true and also totally awesome, so he tries to foil the Hexmajor's efforts. And the commanding officer, General Schneider, has gotten very interested in the advanced technologies described in Kelly's journals, since the hindrance to trade and communication caused by all the petty squabbling has retarded technical advancement in their own timeline. Knecht, however, notes that that advancement also fueled two world wars that his timeline avoided...
This novella includes examples of:
- Alternate History: In this world, the 13 colonies never united, leading to a very different present. Kelly's journal also describes visits to several other alternate histories.
- Alternate Techline: One thesis that Flynn expounds here is that free trade fuels technological innovation, because it means inventions and ideas can circulate quickly and build on each other. The battling states in this timeline inhibited that, so their technology is generally behind ours, though apparently they did invent a few things first, such as plastics.
- Americasia: After one jump, Kelly finds himself facing "armored samurai in a medieval Philadelphia." He has to flee before he can find out how that happened.
- Brainwashing for the Greater Good: Actually, it turns out that the Hexmajor believes he's brainwashing Kelly for his own good, because he'll never get home and he's better off just forgetting about it.
- Chekhov's Skill: At one point, Kelly jumped timelines while riding a horse and found that the horse jumped with him, leading him to realize that the Interdimensional Travel Device's energy field is bigger than he thought. This ends up being important because Vonderberge eventually jumps with him.
- Close-Enough Timeline: By this time, Kelly thinks it unlikely that he'll ever get back to his original timeline, but he's hoping to at least get to one that has his wife in it.
- Day of the Jackboot: In an early jump, Kelly landed in a version of Philadelphia with a swastika flag flying over it, and a nun hanging from the flagpole.
- Divided States of America: While New England formed a confederation, the rest of the colonies turned into independent states. As a result of the disunity, the westward expansion never happened either.
- Hypno Fool: Psychiatry in this world is stranded in the 19th century, so hypnosis is what the Hexmajor uses to try to "cure" Kelly. He mentions that it's also used in stage shows to make people act ridiculous.
- Interdimensional Travel Device: Kelly's device, which he invented by himself, involves some wiring around his waist hooked up to a backpack. Since the viewpoint character doesn't understand it, it's only vaguely described.
- Poirot Speak: Independent Pennsylvania made Pennsylvania Dutch its official language, so when the military men talk with Kelly in English they're speaking their second language. This leads to some awkward grammar—Knecht tends to put his verbs last—and German words dropped in here and there.
- Sanity Slippage: Kelly starts getting mighty confused about reality after the Hexmajor's hypnosis treatments.
- There's No Place Like Home: Kelly saw his timeline-hopping as a grand adventure, but now he just wants to get back.