Aunt Mabel's new client, Stella Harper, is snooty, power-hungry, and treats everyone like a servant - pretty much everything Marcie assumes about rich people, and despises. So when the woman starts receiving letters that say, "P.S. I poisoned you," no one is surprised or even cares too much. Plus, Marcie is pretty sure the woman is sending those letters to herself for attention. The big phony.
That is, until a mysterious death occurs, and Marcie is thrown into the middle of solving another case, this time with the help of her friend Tracey, a woman who seems to think solving a murder is an excuse to relive her "party girl" years in her retirement, while dragging Marcie around with her. Worst Watson ever. But the fun and games end when Marcie and her friend unravel a plot involving an international art forgery ring, Russian oligarchs, and more "P.S. letters."