Daisy Wells and Hazel Wong are taking a holiday on the famous Orient Express. From the moment the girls step aboard, it's clear that everyone in the first-class carriage has something to hide. Then there is a scream from one of the cabins, and a wealthy heiress is found dead. But the killer has vanished - as if into thin air. Daisy and Hazel are faced with their first locked-room mystery - and with competition from several other sleuths, who are just as determined to crack the case.