The conflict is that Mrs. Stevenson hears about a murder over the phone while trying to call her husbands work.
Mrs. Stevenson calls a random number accidentally while trying to call her husbands workplace. After hearing this she tries to track down the number, but is told this can't be done. She calls operators, Sargent Duffy, and even the Weston Union, but it's no use.
She has called basically everyone she can and is now getting frustrated. When she calls the operator to dial the police, she hears a click on the phone, meaning someone else is on the phone and is listening in.
Nervously, she waiting for her killer to arrive hiding in fear.
Killer picks up phone and says, " Sorry wrong number." Then, hangs up.