A Sala Dos Répteis by Lemony Snicket

After a string of unhappy guardians, three resourceful siblings are placed in the care of a kind, eccentric herpetologist who introduces them to a world of reptiles and scholarly curiosity; their temporary peace is shattered when a sinister actor returns in disguise to seize their fortune, a murder is committed, and the children must use their cleverness and evidence to expose the villain—only to be thwarted by indifferent adults and forced to continue their precarious search for safety.