CHICAGO (AP) _ Police said a man stole Henrene Lindsey's car, but quickly abandoned it and called the owners when he discovered a passenger in the back seat: Mrs. Lindsey's 10-month-old baby.

Mrs. Lindsey, 33, had just finished fueling the idling auto and was approaching the cashier window at a West Side gas station when a man drove off in her car, said Patrolman James Nowlin. The woman's purse also was in the car, he said.

After discovering 10-month-old Jerry Lindsey in a baby seat in the back, the thief telephoned Mrs. Lindsey's home and told her husband, Jerry, ''I may be a thief, but I'm no sadist,'' police said.

The thief told Lindsey where he could find the car and his son, but added, ''I will keep the purse,'' which contained $40 and 12 credit cards, police said.

Lindsey rushed to the location the man gave him - about five blocks from the gas station, said Lt. Joseph Mucia.

He found little Jerry sitting in the back seat, wide-eyed and smiling, Nowlin said. The thief was nowhere to be found.

When police arrived, they saw Lindsey opening the car door and grabbed him as he protested, ''No, I'm the father,'' Nowlin said. A squad car then pulled up with Mrs. Lindsey, who assured officers that the man was her husband.