The Great Christmas Pudding Heist features the brand's panda mascot Vinnie enlisting Facebook fans to help find his stolen treasure, which have been smuggled inside Christmas puddings.
Users follow clues on Twitter and Facebook to track the stolen goods. They will point to offline locations in cities across the UK, and participants who track down the bandits at these places will receive a cash prize of £250.
Entrants who solve all of the online clues will win a prize of £125.
The campaign was created by Finn PR and Mother with Facebook activity handled by 20:20.
Wayne Greensmith, marketing manager at Fox's Christmas Puddings, said: "Vinnie is a powerful brand icon and his Facebook fan page has a highly engaged audience, so it makes sense to involve them in the launch of the new product."
Follow Sarah Shearman on Twitter @shearmans