Mercy Island was originally published in 1941. Theodore Pratt was a Florida-based writer and all of his books, including this one, took place in the Sunshine State. The edition above came out in 1953. The cover was by Verne Tossey, who has been featured on the site in the past and who will be featured in the future.
The thing I like about this cover is the facial expressions of the three people involved. The man throwing the punch looks like he doesn’t even know where he is anymore. That shirt is about to get ripped.