When unemployed San Francisco reporter Chuck Townsend and his college dropout son, Justin, take a cruise to Mexico in 2016, each hopes to rebuild a relationship after years of estrangement. But they find more than common ground aboard the ship. They meet a mysterious lecturer who touts the possibilities of time travel. Within days, Chuck and Justin find themselves in 1900, riding a train to Texas, intent on preventing a distant uncle from being hanged for a crime he did not commit.

Weeks after her husband dies in the midst of an affair in 2016, Chicago writer Susan Peterson, 48, seeks solace on a California vacation with her mother Elizabeth and daughter Amanda. The novelist, however, finds more than she bargained for when she meets a professor who possesses the secret of time travel. Within days, the women travel to 1938 and Princeton, New Jersey.

Providence, Rhode Island, 2017. When doctoral student Cameron Coelho, 28, opens a package from Indiana, he finds more than private papers that will help him with his dissertation. He finds a photograph of a beautiful society editor murdered in 1925 and clues to a century-old mystery. Within days, he meets Geoffrey Bell, the "time-travel professor", and begins an unlikely journey through the Roaring Twenties.

When Mary Beth McIntire settles into a vacation house on June 2, 2017, she anticipates a quiet morning with coffee. Then she hears a noise, peers out a window, and spots a man in 1950s attire standing in the backyard. She panics when the trespasser sees her and enters the house though a door to the basement. She questions her sanity when she cannot find him.

After struggling for years to have a child, Claire Rasmussen, 34, turns to adoption, only to find new obstacles on the path to motherhood. Then, she gets an unlikely phone call and soon learns that a distant uncle possesses the secrets of time travel. Within weeks, Claire, husband Ron, and brother David find themselves on a train to Tennessee and 1945, where adoptable infants are plentiful and red tape is short. For a time, they find what they seek. Then, a beautiful stranger enters their lives, the navy calls, and a simple, straightforward mission becomes a race for survival.