When ten-year-old Theo runs off from a school trip to London's Natural History Museum and decides to pay his gran a surprise visit, he discovers the surprise is on him - his gran is on holiday and Theo finds himself alone in the big city with nowhere to turn. Enter Alistair Goodfellow, a mysterious, flamboyant young person with a charismatic twinkle in their eye.

Alistair offers Theo a room at the Casablanca Lily - by day, a run-down and unloved hotel; by night, a palace of magical wonders. Each night, Alistair sends their found family of runaways and ne'er-do-wells, the Moonlighters, out into London in search of lost magical artefacts, gifting them their own magical powers as a reward. Theo is quickly enthralled, but there is more to Alistair than meets the eye, and soon Theo comes to realize that the items Alistair is hunting could be more dangerous than he'd ever imagined .