When Uncle Ben's Dublin business fails, Gloria and Raymond realise that something is wrong. So when the children overhear their granny saying that the Black Dog has settled on Ben's back and he won't be OK until it's gone, they decide they're going to get rid of it and they set out on a midnight quest to hunt it down and chase it away. But loads of other children are searching for it too, because the Black Dog is hounding lots of Dublin's adults. Together the children manage to corner the Black Dog ... but will they have the courage and cleverness to destroy the frightening creature?