Destroying Angel - S1.E2

A man is found dead in his room above a sleazy bar and brothel. Van der Valk is called in when the examining doctor suspects poisoning. Immediately sensing there is more to the case than meets the eye, he uncovers a complicated web involving drug dealing and the grubbier end of Amsterdam's S & M industry. Ultimately though, he finds the motive for the man's murder may lay elsewhere and that ""Destroying Angel"" is definitely involved; but who, or what, is that?