[4] In 1912, Edwin St. John St. Andrew, youngest grandson of an English earl, scandalizes his father at a dinner party by criticizing the British Raj, and is exiled to Canada as a remittance man.

Beset by ennui toward Victoria's similarity to English high society,[5] Edwin travels to Caiette, a fictional settlement (which also appeared in Mandel's previous novel The Glass Hotel) on the sparsely-inhabited Vancouver Island.

[4][2] Paul plays a childhood video filmed by Vincent in which, like Edwin, she is momentarily transported from a forest to a dark, train station-like space where a violin is heard.

[4] Then, as a man named Gaspery-Jacques Roberts (who accidentally betrays foreknowledge of the COVID-19 pandemic) questions her about the video, Mirella is disturbed to recognize him, seemingly not having aged, from a traumatic murder scene which she witnessed as a child in Ohio.

[4] She headlines numerous media events and lectures, promoting her breakthrough novel, Marienbad, about an imaginary influenza pandemic; all the while, reports of a string of real-world viral outbreaks escape her attention.

[2][4] His prodigy sister, Zoey, who followed in their late mother's footsteps as a physicist, confides in him her research into Edwin, Vincent, and Olive's experiences of having swapped places, impossibly, across centuries.

He witnesses the anomaly at the same time as Vincent, then travels to 1918 to accomplish his true goal: to personally assure Edwin of his sanity, saving him from being committed to an insane asylum.

[8]: 219  Returning to the Time Institute, Gaspery-Jacques is arrested alongside Zoey, but he does not regret his actions even upon learning that Edwin's ultimate death from the Spanish flu remains unchanged.

[9] Decades later, having learned the violin and moved to Oklahoma City, Alan plays at the Airship Terminal on the destined day, seeing reality corrupt and repair itself as Edwin, Vincent, Olive, and his past selves all appear before him.

[4] An example of this is a sentence detailing the human experience of the pandemic: "the panic, the lockdown, the constant sirens, technology exhaustion, the shifting and rethinking of personal and career priorities.

[11] Yvonne C. Garrett has called Sea of Tranquility in The Brooklyn Rail "beautifully written" being an "equal parts vast and intimate, quiet and thrilling contemplation on humanity, physics, time, and what it means to be alive.

"[12] Writing in the Financial Times, Christian Lorentzen sees the work in a clearly negative light: He argued that "Sea of Tranquility is a book where every new element subtracts from the reader’s experience.