Born in Bath, New Brunswick, Canada, in 1922, Charlotte (Matilda) MacLeod emigrated to the United States in 1923, and became a naturalized U.S. citizen in 1951. She attended the Art Institute of Boston. During the late 1940s and early 1950s, she worked as a copy writer for Stop and Shop Supermarkets in Boston. She eventually moved on to join the staff of N. H. Miller & Company, an advertising firm, where she rose to the level of vice president, and retired in 1982.
While continuing to work at the advertising company during the day, MacLeod began writing mystery fiction, eventually publishing over 30 in all. Many of her books are set in New England, including one series focused on college professor Peter Shandy, and another on Beacon Hill couple Sarah Kelling and Max Bittersohn. Other mysteries, set in Canada, were published under the pen name Alisa Craig. She specifically tailored her books to be "cozies", i.e. avoiding too much violence, gore, or sex. All feature a humorous and literate-yet-light style, likable protagonists, and eccentric casts of secondary characters.
Described as a "true lady" and often seen with hat and white gloves, MacLeod began writing at 6 a.m., continued through the morning, then used the afternoon for rewrites. She only started new books on Sundays and during writing would stay dressed in a bathrobe to avoid temptation of leaving the house for an errand. Her work sold over one million copies in the United States as well as Canada and Japan. MacLeod was co-founder and past president of the American Crime Writers League. She received a Nero Award for The Corpse in Oozak's Pond (1987), which was also nominated for an Edgar Award.
MacLeod spent her final years in Maine. Toward the end of her years she suffered from Alzheimer's disease and died on January 14, 2005, in a Lewiston, Maine nursing home.