The Angel of Mercy Hospital is an abandoned hospital where Harry Morgan's father worked as a Janitor, before "working his way up to Chief of Maintenance."
This is also where the Ice Truck Killer holds Tony Tucci hostage and performs live amputations on him, leaving the body parts in public places that are reminiscent of Dexter Morgan's childhood (such as Petrie Beach and the McCaffrey Pumpkin Patch).
Dexter soon finds Tucci in this building, abandoned, cut up and begging for a merciful death, but he decides to free him rather than end his life.
Gallery
Dexter finds Tucci in the hospital.
Brian's kill tools left behind for Dexter to kill Tucci.