After Tom Rehberg (Helmut Zierl) in “REDLIGHT” and REDLIGHT – THE FENGLER FILE” fought successfully against organized prostitution, he is now acting as a special agent in Berlin’s redlight district. Together with his assistant Oliver Jürgens (Arndt Schwering-Sohnrey) they shadow Diana Monte, the erotic-queen owner of “Diana Entertainment”, since they believe she runs illegal child-prostitution ring that’s covered by her legal erotic internet-site. Using a codeword, Tom arranges a meeting with one of the underaged girls. He chooses the brothel “Cupido” for this meeting. The “Cupido” is owned by Maren , the best friend of Tom’s girlfriend Anna. After the horrible experiences Maren has had as a prostitute, she decided to shelter other prostitutes in her “Cupido” and give them real work-contracts. Anna supports her friend and promises to look after the “Cupido” if ever something should happen to Maren.

Tom waits for the girl in vain – it looks like his investigation has come to naught. His old friend and colleague Werner Horn puts him on the trail of a Ukranian slave trader named Gerassim. Tom shadows him and notices a meeting between him and Maren in a shack. Before he can even intervene, the shack explodes, killing Maren while Gerassim is able to escape. Anna keeps her promise and her commitment to the “Cupido”. Tom cannot comprehend her decision, so a conflict erupts between the two.

With the help of an old informer, Tom finds Gerassim. The Ukranian acts as if the whole thing was a put-up job against him. Tom believes him instinctively. Before he is able to share this with Horn, Horn shoots Gerassim because he believes Tom is in danger of being murdered. Tom is more and more convinced that there is something quite wrong with this case. By the time he reaches the surprising solution, he and Anna have to face two painful disappointments.