As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEVEL 3 ALERT CABIN SMOKE. AFTER DEPARTING, AT ABOUT 20 MINUTES OR SO INTO THE FLIGHT AND AT 33K FLIGHT ALT "LEVEL 3" CABIN SMOKE ALERT DISPLAYED ON EAD. RETURN TO DEPARTURE. FOUND CONDENSATION IN MAIN CABIN COMING FROM PACK NR 2. R & R COALESER ON PACK NR 2 IAW 21-54-04. OPS CHECK OF CARGO SMOKE DETECTORS, OPS CHECK PASSED NO FURTHER CONDENSATION NOTED, ACFT RETURNED TO SERVICE.