Alberta Murray may be young and inexperienced in life, but she knows her husband didn't commit the murder he's accused of, so she sets out to prove his innocence -- even though he was cheating on her with another woman. Kirk Murray's lover was Mia Mercer, a showgirl with many admirers. Alberta goes to Mia's apartment to confirm her suspicions about her husband's infidelity, only to find the woman dead.
She returns home, and so does Kirk -- with two police officers. He's been arrested for Mia's killing, and only a few weeks later is convicted and sentenced to the electric chair. But Alberta never believed he could have been the killer. She remembers a clue from the crime scene, a matchbook cover monogrammed with the letter M, and sets out to find the men from Mia's address book whose names begin with M.
The first she finds is Marty Blair, an alcoholic husk of a man lurching from bars to flophouses and back again. He loved Mia long ago, but he isn't the killer. The second is Dr. Mourdant, for whom Mia had been delivering illegal drugs. Alberta fills in for one shift of this work. She and the doctor are both arrested, but a sympathetic detective has her freed.
Alberta continues her investigation, locating the third name in the book, Ladd Mason. She finds a matching monogrammed matchbook at Mason's home, and with the detective, sets a trap for her suspect. Mason admits he went to Mia's home the day of the murder but didn't kill her: by the time he got there, she was already dead.
The final M is McKee, a nightclub owner who falls in love with Alberta. She finds evidence against him at his home, but she he catches her in the act, he sends her out to be killed by his goons. Alberta is able to call Mason to save her, since he still loves her. But she reveals to him that she is till true to Kirk -- and he reveals that he killed Mia after all. He attacks Alberta and suffers a seizure at the same time, then kills himself by leaping out the window. In the final scene, Kirk is free and back home with Alberta, who can't shake the feelings she had for Mason.
Best part of story, including ending:
Woolrich's language is stunning; despite being archaic at times, he paints scenes so dark and pungent you start to believe Alberta really has gone to some Dante-esque level of hell.
Best scene in story:
When Alberta tracks down her first suspect, Marty Blair, in a depressing Bowery dive bar, she can feel the eyes of everyone else in the bar as she walks across the floor to meet him. She describes a hand reaching out to her as that of one condemned, only to pull back at the last moment, as if aware there was no hope for redemption in a place such as this.
Opinion about the main character:
Alberta starts out shy and retiring, but she has wells of strength she doesn't know of, facing down killers and thinking on her feet in even the most dangerous of situations. She remains an impressive heroine.