A door is locked in the closed position by a system of five bolts which can be simultaneously operated from either side of the door by a handle or key operator. Both the handle and key operator are common to all of the bolts in the system and are connected through a rotary camming device with a linkage including parts drivingly connected with the bolts. A lost motion connection is provided between the key operator and rotary camming device to enable complete rotation and withdrawal of the key. The linkage and bolts are protectively enclosed inside of tough conduits and linkage access housings. A safety bolt immobilizing device is provided on the door adjacent to one bolt of the locking system to block the extension of the bolts while the door is open and this device moves automatically to a bolt release position when the door is closed. The locking system can be placed in a residential door or may be installed on a commercial door.