A 25-year-old Dubuque woman was treated at Mercy Medical Center early today for injuries she received when she was struck with a blunt instrument by an unknown assailant at 3:15 a.m. Darlene Schlarman, of 1196 Thomas PI., told police she was on her way home when the rear of her car was bumped by another car at the intersection of Fengler Street and Lincoln Avenue. Miss Schlarman told police she got out of her auto talked to the driver of the other car and then drove home. Police said the man followed her home and as she was locking her car he hit her with the blunt instrument. She was released from the hospital this morning. Police are continuing their investigation.