It's an ordinary, dreary February morning when journalist Amanda Griggs is rudely awoken by her boss after yet another night of mindless hedonism. 'Yellow!' he barks down the phone. Yellow? Yellow what?

It doesn't take long to find out, for this morning London is wearing a big, yellow smile, and her inhabitants seem to find it catching. All around the town, yellow insignia have popped up: The Monument wears decadent yellow streamers, Temple Bar proudly displays enormous yellow rosettes, Queen Victoria's statue is regally crowned with a wreath of daffodils. Amanda is on the case, as is DCI Prior, but what exactly is the case? Can this cheerful hoax really be as harmless as it appears? And what does it signify?

A series of bizarre events ensue, culminating in criminal theft on an enormous scale. Clearly this is the work of no ordinary thieves but an organised gang seeking maximum publicity, but what on earth could their motive be?