On a moonless night on Sanibel Island, Florida, marine biologist Marion "Doc" Ford carefully watches a video of a hooded man executing three hostages. The man is an American working with ISIS, and in the next few days, it'll be Ford's job, as part of his shadowy second life, to make sure he never kills anybody else again. But a lot can go wrong in a few days, and Ford has no way of knowing that not only will the operation prove to be a lot more complicated than he has anticipated, but that he'll end up bringing those complications back with him to the small community of boaters, guides, lovers, and friends in Dinkin's Bay, where he's long made his home.