Death Pact — William Manchee

An attorney is appointed trustee over a seventeen-year-old girl's estate. They fall in love and enter into an illicit affair. When the girl's sole relative discovers them and threatens to get the attorney disbarred and sent to jail, she is murdered and the two lovers become prime suspects. Rather than risk separation and a life apart, they vow that if either is convicted they will both take a cyanide pill.