The Bletchley Circle (2012)

Lack of action by the police leaves the women to conclude there must be corruption within the vice squad and that catching the gang red-handed is their only option. Plotting to infiltrate the crime ring to find out the location of the hotel being used as a base, they visit Marta in her restaurant, pretending Jean is a potential new client. This leads to an opportunity for Lucy to memorise the businesswoman's ledger, which may hold the key to the whole operation.