Shortly after leveling off and beginning the cruise portion of the cross-country flight, the engine lost all power. The private pilot/owner performed a forced landing on a highway; however, just before the landing flare, the airplane’s vertical stabilizer struck a power cable and partially separated from the tailcone. Postaccident examination of the engine revealed that the carburetor drain plug was missing. The pilot stated that he had flown the airplane using automotive gasoline about 2 months before the accident. When the engine was subsequently difficult to start, the pilot removed the carburetor drain plug to purge the system of automotive fuel. He stated that he did not use safety wire to secure the plug after performing this operation. Maintenance personnel examined the carburetor after the pilot reported that the engine was running rough (about 2 months before the accident) and again during the airplane’s annual inspection (about 1 month before the accident). Although maintenance personnel reported that on both occasions the drain plug was secured with safety wire, physical evidence suggested that the drain plug had never been secured with safety wire. Because of the contradictory statements and inconclusive evidence, it was not possible to determine who was responsible for the unsecured drain plug.