Islands had been disappearing - under the worst floods ever known. Natural disasters? Or something much more sinister? Dr. Palfrey was not alone in fearing the latter?

Was it mere coincidence that Sir Gabriel Davos, the research scientist, had been in the vicinity of each island before it was overtaken by misery? And what were the mysterious crab-like creatures that had invaded the islands in their thousands?

One thing Palfrey did know - that unless he acted soon, the whole of Great Britain might be threatened. Not merely with floods, but with extinction!