As a suspense mystery this was alright but the side characters - especially Mary (Victoria Roc) has been extremely weak in depiction. In the original novel itself it was too weak - she was ready to hop in the bed of Meister despite being well aware of the things - but there a bit of black-mail was involved - though that wasn't probably enough to warrant her 'sacrifice'. Here even that didn't exist. In addition, it wasn't known how the hidden pathway to his home was known to every one, except the cops of course. Probably a better adaptation was called for. Converting a full novel into a movie is a difficult proposition, a lot of nuances have to be brought in, to justify the actions of every one.
I found the other famous work "The Forger" was better adapted - in German version, Der Fälscher von London - except a minor modifications - one in relationship - John Leith was uncle rather than father of the heroine - and of course the end was slightly changed. But that didn't change much of the 'sense' of the novel and its characters.
That aspect was missing here. Of course two main characters can't be faulted on this count - the shrewd doctor-detective Lamont and the 'Weasel' after the rabbits, 'Meister' .