Jamie Winton (Mathew Baynton) works as a bank manager in Slough, England, living with his best friend, Dave Bosley (Joel Fry), and his adoptive mother, Paula (Pauline Quirke).

Jamie vows to find his wife, Layla (Karla Crome), who disappeared seven years ago, and his biological mother before the comet hits.

Meanwhile, Rhonda McNeil (Jenna Fischer) is imprisoned in New Mexico, United States, after taking the blame for a hacking crime committed against the National Security Agency by her son Spike (Fabian McCallum).

In Washington, D.C., Rhonda's brother Scotty (Kyle Soller) and his husband, U.S. General Arnold Gaines (Paterson Joseph), are working to stop the comet that will cause the apocalypse.

At the Vatican, Father Jude (Rob Lowe) and Sister Celine (Gaia Scodellaro) work to find the potential Antichrist and the world's savior.

Rhonda is terrified of her new surroundings and inmates but refuses to give up her son, Spike, who actually did the hacking, and faces the rest of her life in prison.

However, as the apocalypse is announced, a riot breaks out and Ariel appears to hack into the prison system to rescue Rhonda, as well as Leanne who stowed away.

The president seeks the advice of General Arnold Gaines and Scotty McNeil, Rhonda's brother, who specialise in end of the world disasters for the US government.

Scotty and Gaines begin Project Saviour, an operation using the world's finest minds to stop the comet hitting Earth.

Meanwhile, Frankie hears voices in her head and rescues Jamie from the bank vault with the recently married Paula and Dave.

Just outside Slough, Jamie, Layla, Frankie, Celine, Paula and Dave are stuck on one side of the River Thames after the bridge is destroyed by debris.