Searching for a few weeks now

[Sybaris_Caesar]

The guy's a private detective. His sister's his assistant. The sister is thirsty for him but he won't give in. A sexy wealthy client walks in with her brother methinks. Don't remember the particulars of the case. A noir adventure. Turns out the client was fucking her brother and her father. Mother was long dead. Possibly after finding out about daughter and husband. The private dick is in an abandoned house. Client was tied up iirc by the brother. But actually her twin sister (mental patient or sth) has killed their brother for a few weeks and masquarading as the brother. Now captured her sister. Gets the mc tied up too. Kills the client in front of him, shoots him and burns down the house. Luckily the guy's alive. His sexy sister nurses him back to full health and makes love to him. The guy won't resist anymore. The psychoo twin is still at large.