The Third Rule of Time Travel by Philip Fracassi

Published by Orbit on March 18, 2025

Time travel stories can be fun but doing them right can be tricky. Authors usually take note of the paradox — kill your grandfather in the past and you never come into existence and thus can’t travel to the past to kill your grandfather — but they don’t always address it effectively. One approach is to avoid the paradox by traveling to the future. Another is to travel observationally, watching the past through a lens without interacting with it and thus avoiding changes. Another is to travel to the past with the intent to change nothing, usually followed by a mishap that changes everything. Another is to have the traveler change something that doesn’t prevent her birth and then returning to the past to undo the change. Another is to assume the existence of multiple time streams, so that changing the past either shifts the observed reality into a different stream or begins a new one. Perhaps because The Third Rule of Time Travel incorporates all these approaches to varying degrees, it fails to tell a convincing story.

Beth Darlow and her husband Colson invented a time travel machine. The device opens a wormhole that transports the traveler’s mind into her body at an earlier time. The two minds cohabit in the traveler’s past body although (for reasons left unexplained) the past mind doesn’t seem to recall the visit from future self after the experience ends. The mind transported from the present, on the other hand, is aware of the past mind and recalls what she observed through her past self’s eyes. The only physical evidence that two minds are sharing a body is a whitening of the eyes in the traveler’s body while it’s inhabited.

The travel ends after ninety seconds. A skeptic might think that the machine is merely stimulating memories and not transporting the traveler, but evidence (other than the temporary change of eye color) eventually emerges to suggest that a mostly useless form of time travel has actually occurred.

Colson died in a car crash, leaving Beth to further the research and to replace him as the time traveler. Beth is trying to understand how the time machine chooses arrival points. She thinks that directing time travel to a specific date will make the machine more useful, but the traveler will still observe only the things she has already seen. I can imagine some scenarios where that might be helpful (a crime victim who can’t identify an assailant might notice more details when revisiting the assault), but a lot of money is being invested in technology that hardly seems to justify the cost.

The research is funded by a creep who wants profitable results. His efforts to attract new investors cause Beth to take risks. This leads to an inevitable confrontation between the investor, who believes he has exclusive rights to the invention, and Beth, who is one of the few people who understand how the contraption works. It turns out that her understanding is less than complete.

When Beth begins traveling, she notices that the machine always sends her back to traumatic moments in her life, including identifying her husband’s body in the morgue. Beth eventually realizes why that’s happening, but the explanation [spoiler alert] amounts to “the universe doesn’t like to be messed with.” Nonsense of that sort bleeds the science out of science fiction.

Beth begins to see the ghost of her dead husband. Then she changes the past in a way I won’t spoil. How she does that is never made clear, a startling omission since one of the titular rules is that travelers can’t interact with the past and thus can’t change it. I guess we’re supposed to accept the theory that observing a quantum system causes it to change, but the application of that theory to the plot is disappointingly fuzzy.

Beth only knows the past was changed because, before she travels, she sends answers to certain questions to an off-planet location where they won’t be affected by any changes to Earth history. (This has something to do with the inverse square law and the assumption that the machine’s energy pulse will lose its energy as it travels away from the Earth, leaving the pre-recorded answers invulnerable to change.) The story’s tense moments result from Beth’s desire to undo the changes she made and the owner’s desire to stop her from revealing the harm that his useless but expensive technology might cause.

The setup is interesting even if Beth isn’t. The story’s resolution combines metaphysical gibberish with simplistic pseudoscience. Now, there’s so much we don’t understand about the universe that maybe Philip Fracassi got it right, but other writers have made a more convincing case [second spoiler alert] that time is an illusion, that there is only the now, and that the now encompasses all possible pasts and futures. This convenient theory empowers Beth to construct the reality she wants and thus enables a happy ending, but science fiction’s demand that readers suspend their disbelief needs to be supported by a plausible reason to do so. Metaphysical gibberish about an angry universe and simplistic pseudoscience didn’t get me there, particularly when the ending doesn’t address the many ramifications of the story’s underlying theory.

That leaves us with a conventional thriller — a race to save the present by undoing changes to the past — surrounded by the trappings of science fiction. This science fiction thriller is more effective as a thriller than as science fiction, but the thriller aspects are unoriginal. Thriller fans might nevertheless enjoy it. Hardcore sf fans, not so much.

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