Abstract: In an apparatus and method for deterring and preventing forced entry intrusion into residential and commercial premises, the apparatus is a combination vertically operated dead bolt door lock surrounded by an alarm housing having battery means, a loud speaker, and a contact switch. The lock striker plate is mounted to the door frame as usual, but the lock is not mounted to the door at all, but rather is attached in suspension within the alarm housing. The alarm housing is attached to the door, and the lock within the housing is offset so as to float in spaced-apart relationship from the door on which the alarm housing is installed. Upon an intrusion effort, the door, together with the alarm housing will be shoved inward toward the premises by the intruder. But the lock floating within the alarm housing will be restrained by its engagement with the striker plate mounted to the door frame.