Tom Jimson, the burglar has $700,000 stashed away in a valley town, which has been converted into a reservoir, by the state of New York. Now, the money lies fifty feet below water and the only way in which Jim wants to retrieve it is to blow up the dam. With the fate of nine hundred people at stake, it falls on John Dortmunder to formulate an alternate plan for retrieving the loot. And, as each attempt by Dortmunder fails, Tom's dynamite finger gets itchier... and itchier.