Abstract: An overhead socket smoke detector with a theft alarm includes a case with a bulb base at one end and a lamp socket at an opposite end and connected to the bulb base by a socket switch which is closed by a lamp received in the socket to electrically activate the socket. The case has a cylindrical diameter to fit within a can light fixture. Smoke alarm circuitry is mounted within the case and includes a smoke sensor circuit, a trigger circuit, and a sounder circuit. A unit removal or theft switch connected to the trigger circuit includes a switch operator extending through the bulb base to engage a socket into which the case is threaded. A rechargeable battery and a battery charger are connected between the bulb base and the alarm circuitry and provide power to operate the alarm circuitry. When the unit is removed from its fixture, the unit removal switch disengages the fixture socket and triggers the sounder circuit into activation to deter removal of the unit from the socket in which it is mounted.