A is For Alibi is a 1982 crime novel by Sue Grafton, the first in her "Alphabet" series. The novel follows detective Kinsey Millhone, who investigates the murder of Laurence Fife, for which his wife had been imprisoned. The investigation leads Kinsey to other murders of the same strange method (the poison oleander). Eventually the case is unravelled and she discovers that Scorsoni, a man whom she was involved with and who was Fife's business partner, is a murderer. In a confrontation on the beach she kills him.
"A" Is for Alibi features Kinsey Millhone, 32, a private detective. She investigates the death of prominent divorce lawyer Laurence Fife. His murder eight years earlier was blamed on his wife, Nikki Fife, who upon being released from prison hires Kinsey to find the real murderer.
In the course of the investigation Kinsey becomes involved with Charlie Scorsoni, Fife's former law partner. She discovers Fife's death has been linked to that of a woman in Los Angeles, his law firm's accountant; both died after taking poisonous oleander capsules which had been substituted for allergy pills. Kinsey tracks down the accountant's parents and former boyfriend. She then goes to Las Vegas to interview Fife's former secretary, Sharon Napier, who is killed minutes before Kinsey arrives.
Back in California, Kinsey is mystified that Nikki's son, Colin, recognizes Laurence's first wife, Gwen, in a photograph. Kinsey surmises that Gwen was having an affair with her ex-husband at the time of his death. She accuses Gwen, who confesses. Shortly afterwards, she too is dead, killed in a hit-and-run crash.
Kinsey has solved the case she was hired to investigate, but in a plot twist, she discovers that her previous notions about the accountant's death were entirely wrong: in fact, it was Scorsoni who killed her when she discovered he was embezzling money from mutual accounts. He used the same method that Gwen used to kill Fife, so it would be assumed the same person committed both murders. In a final confrontation, he chases Kinsey across the beach, armed with a knife. Before he can kill her, she shoots him dead.