Arsenic for Tea (A Murder Most Unladylike Mystery) -- Paperback

Schoolgirl detectives Daisy Wells and Hazel Wong are at Daisy's home, Fallingford, for the holidays. Daisy's glamorous mother is throwing a tea party for Daisy's birthday, and the whole family is invited, from eccentric Aunt Saskia to dashing Uncle Felix. But it soon becomes clear that this party isn't really about Daisy at all.