Shutter Island by Dennis Lehane

The year is 1954. U.S. Marshal Teddy Daniels and his new partner, Chuck Aule, have come to Shutter Island, home of Ashecliffe Hospital for the Criminally Insane, to investigate the disappearance of a patient. Multiple murderess Rachel Solando is loose somewhere on this remote and barren island, despite having been kept in a locked cell under constant surveillance. As a killer hurricane relentlessly bears down on them, a strange case takes on even darker, more sinister shades—with hints of radical experimentation, horrifying surgeries, and lethal countermoves made in the cause of a covert shadow war. No one is going to escape Shutter Island unscathed, because nothing at Ashecliffe Hospital is what it seems. But then neither is Teddy Daniels.