Sweater Girl.

Susan Lawrence develops a romantic interest in Jack Mitchell, who also sings, while their friend Louise Menard is seeing Susan's brother, a professor. All are shocked when songwriter Johnny Arnold is strangled and school reporter Miles Tucker poisoned with glue from an envelope. One night Jack volunteers to look after Louise's mother, a helpless invalid. Susan becomes worried and, when she arrives, Mrs. Menard tries to help Jack, who has narrowly avoided being killed.