What was even worse was that Luca didn't actually kill the baby. He ordered Filomena, the midwife who delivered the baby, to throw the baby in the furnace of the home where the baby was delivered. She balked, but Luca threatened her with a knife. Luca later killed the mother, was arrested for that murder, tried to cut his wrists in his jail cell. Filomena ran to Don Corleone for protection. Luca didn't work for the Don then, but he protected her by arranging to get Luca out of jail, at which point Luca became devoted to him. It's a great story that only appears in the novel.