Glendon Baker is an invalid who is being taken care of by a nurse named Stella Crosson. Stella is pleased when another nurse named Betty Ames arrives to assist her in the work. The only other people in the house are a house keeper named Maude and her handyman husband Sam. Stella becomes worried when she hears that a nurse killer is in the area. She grows more uneasy when the lights go out. When a patient's oxygen begins to run low, Stella sends the handyman out to get some. Growing paranoid, Stella locks all the windows in the house but neglects to lock the one in the basement. Later, Stella sees a man outside and panics when there is knocking at the door. She fails to notice that it is the handyman trying to get back in. She heads for the phone, but stops and heads into the lounge to help Nurse Ames who has been apparently attacked. Once in the lounge, however, Nurse Ames attacks her.