[2] In-universe audio recordings tell the story of Dr. Sally Grissom, a scientist from the present day that accidentally invents time travel and is sent back to the USS Eldridge in 1943.

[5] Modern-day scientist Dr. Sally Grissom accidentally sends herself back to 1943, finding herself aboard the USS Eldridge during the Philadelphia Experiment.

She is recruited by the United States government to continue developing this new time travel technology under a secret branch of the government called the Office of Developed Anomalous Resources (ODAR), with the goal of using this technology to help the United States win World War II and the Cold War.

[2][3] Grissom and her colleagues find themselves entrenched in politics and interpersonal struggles as they work to repair and improve their time travel device, the Timepiece, and avoid changing too much of the past.

They discover that time travel causes an illness called Butterfly Syndrome, which causes brain damage that makes individuals constantly switch tenses while speaking.