Arthur Penhaligon is supposed to die and he almost does on a school run when he collapses because of his chronic asthma. In his dreams he is visited by the enigmatic Mister Monday, who gives him a mysterious atlas and a magic key shaped like the minute hand of a clock. But Arthur wakes up and Mister Monday wants everything back. With these "gifts", Arthur suddenly assumes new powers and with them frightening responsibilities. Arthur's family and friends are under threat from a sudden outbreak of drug-resistant influenza and it seems the cure to this curious rash of afflictions can only be found inside a vast house that only Arthur can see.

Arthur has no option but to step inside and in doing so becomes the world's most unlikely hero and champion. Battling obstacles such as dog-faced Fetchers and people with Wings, robots and unbreakable chains, Arthur fights to stay intact and for meaning to this crazy world he has tumbled upon.