In her mid-eighties, retired school teacher, Matilda Thistlethwaite lives each day to the fullest. Keeping her body in fine fettle with yoga exercises, church and community activities, and good-hearted meddling, Tillie, as she is known to her many friends, works to keep her mind sharp with a regimen of "cerebral calisthenics", a seemingly endless series of self-improvement classes. However, whether leading a senior citizens' yoga class, baking boxes of yummy treats for the town's public servants, learning an obscure language, or practicing the bagpipes, Tillie always has time for friends and neighbors. All her efforts seem to be working until she shares a bus stop with a murder victim...or does she? When the body mysteriously vanishes, Tillie is hard pressed to convince anyone of what she's seen. Unable to explain what happened, she even begins to doubt herself. No one can stay young forever. Has old age finally caught up with remarkable Mrs. T.?