As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS NOT DECLARED DUE TO: ZONE-E TEMPERATURE INCREASED AIR CONDITION RESET FAILED ADDITIONALLY MULTIPLE SMOKE ALARMS SOUNDED AND SMELLED SMOKED IN FIRST CLASS CABINS; AIRCRAFT AIR INTERRUPTED BACK TO AND LANDED SAFELY AT BOS. ODOR SOURCE IN CABIN AND FLIGHT DECK, TROUBLESHOOT PER TSI 0092772 APU WAS FOUND TO BE SOURCE OF ODOR. APU REMOVED AND REPLACED. PER WORK CARD 72L31049008.