Retired angel Aziraphale and retired demon Crowley’s lives are upended when a visitor arrives on the doorstep of Aziraphale’s bookshop, bringing chaos. Local shopkeepers Maggie and Nina get locked in to Nina’s coffee shop when Crowley loses his temper. Heaven and Hell are suspicious, and Crowley and Aziraphale have a disagreement.

Heaven and Hell are determined to find the missing angel. An overheard song provides Aziraphale with a Clue. Crowley and Aziraphale visit the pub to discuss ways that humans fall in love. While almost 5,000 years ago Crowley is sent to inflict punishments on the righteous Job, God’s favourite person, as Aziraphale learns at first hand about temptation, and what Gabriel will and won't believe.

Heaven sends the angel Muriel in disguise to spy on Aziraphale and Crowley. Aziraphale drives to Edinburgh in pursuit of his Clue, and learns a little about a lot. The couple’s visit to Edinburgh in 1827 involves graverobbery, a statue and an unfortunate encounter with a vial of laudanum. In the present, Crowley is in charge of the bookshop, and is disappointed by human beings and the weather.

Aziraphale’s good deed of picking up a hitchhiker on his way back to Soho, proves to be a serious mistake. In 1941 Crowley and Aziraphale encounter some surprising adversaries, old and new, as the Nazi spies who almost entrapped Aziraphale return as Zombies from the dead, intent on preventing him from attempting a Bullet Catch on the West End Stage.

Aziraphale tries to bring Maggie and Nina together by organizing a meeting of the Whickber Street Shopkeepers and Street Traders Association. In Hell, Shax is determined to launch a full scale attack on the bookshop, with a legion of demons at her command. Nina's heart is broken, as is a bookshop window. Gabriel has a close encounter with Mrs Sandwich and a small plate of cakes.