Shutter Island by Dennis Lehane
A widower named Marshal Edward “Teddy” Daniels along with his partner Chuck Aule go on a ferry ride to Shutter Island, which is home to Ashecliffe Hospital for the crazy people, to explore how one of the patients vanished, Rachel Solando (who was captivated for drowning her three kids). She flees from the hospital from the isolated hospital, in spite of the fact that she was kept locked with someone or the other to keep an eye on her.
Teddy tells Chuck about the code, he assumes the code points to be of the 67th patient, but the records are only of 66 patients. Teddy also wants to pay back the death of his partner, Dolores, who was killed two years back by Andrew Laeddis, who he assumes to be a patient in the same hospital. The novel is filled with graphics describing WWII. After a Carol hits the place, Chuck and Teddy are exploring, ward C, in which Teddy assumes government tests to take place.