'The dogs of Doggeroo are mysteriously losing their collars. At first Jack assumes they are being careless, but it soon becomes obviously there's more to it than that. Jack goes undercover as a careless, trusting dog to try to un-cover the culprit, but no matter what he does, he can't seem to lose his collar. That is, until Sarge borrows it to put on Shuffle the Pug! Finally, Jack discovers the truth and he and the dogs of Doggeroo take action.' (Publication summary)