In Madrigals and Mayhem, the fourth in Elizabeth Penney's charming Cambridge Bookshop series, Molly Kimball finds that even the holidays can come with a healthy dose of mystery.

Molly is eager to experience her first English Christmas with family and friends now that she's adjusted to her move to Cambridge and her restoration of her family's ancestral bookshop, Thomas Marlowe--Manuscripts and Folios. When local toyshop Pemberly's Emporium reopens, Molly is excited to meet the new owner, Charlotte Pemberly, who is determined to make the toy store a success after unexpectedly becoming her grandfather Arthur's sole heir.

Arthur's new wife Althea Winters and her unpleasant family loathe Charlotte for inheriting what they believe was theirs and have set their sights on a valuable Madame Alexander doll that's gone missing. When Althea's grandson is poisoned by cakes from Tea & Crumpets, Charlotte becomes the top suspect. Molly believes Charlotte was the intended victim and investigates the Pemberly's home, only to discover that Arthur had been murdered.

To get closer to this treacherous family, Molly and her boyfriend Kieran go undercover by volunteering to act and sing for a madrigal dinner directed by Althea and her daughter at St. Hildegard's College. Molly must help her new friend clear her name while searching for the missing doll and wrangling her own family during the chaotic holiday festivities at the bookshop.