Shutter Island by Dennis Lehane

In the year 1954, U.S. Marshall Teddy Daniels and his new partner, Chuck Aule, came to Shutter Island, home of Ashecliffe Hospital for the Criminally Insane, to investigate an unexplained disappearance. Multiple murderess Rachel Solando is loose somewhere on this barren island despite having been kept under constance surveilance in a locked, guarded cell. As a killer hurricane bears relentlessly down on the island, hints of radical experimentation, and covert government machinations add darker, more sinister shades to an already bizarre case. Because nothing in Asheville Hospital is remotely what it seems.