As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD INFLIGHT - CREW REPORTED FIRE ALARM SOUNDED AT LEFT MID LAVATORY WITH STRONG ELECTRICAL ODOR IN MID CABIN NEAR CEILING. CREW DISCHARGED 3 HALON BOTTLES. RETURNED TO ORD AND LANDED WITHOUT INCIDENT. NO EVIDENCE OF FIRE. FOUND AIR INLET RESTRICTED AND FAULTY SMOKE DETECTOR. CLEANED AIR INLET AND REPLACED SMOKE DETECTOR AT LEFT MID LAVATORY. ACCOMPLISHED PACK BURN. SYSTEM GROUND CHECKED NORMAL OPERATION.