Pittsfield, Hls., April 17.- Mrs. Lou Plaisneyer shot and instantly killed her stepson. She had ordered him to go and help her husband do some work. This enraged yonng Plaisneyer and he advanced toward his stepniother with a knife, whereupon Mre. Plaisneyer secured a revolver and shot him. Young Plaisneyer was about 38 years old and hiB steprnother 68.