Twins with an ambiguous past arrive on the late 60`s swinging London underground scene (something I have a weakness for, and plays an important role in determining whether you'll enjoy this film or not) and get caught up with a dubious clan of characters, one of whom has an unpaid gambling debt. He's trying to maintain a low profile while trying to shag the female twin and play Alpha male at the mod scenes and, of course, isn't successful at either.
The male twin has a sexual penchant as well as a possible sexual past with his sister, which is why this flick is remotely interesting. Martin Potter (Fellini`s 'Satyricon') steals every scene he's in, and is the best reason to see this one. He also has too much involvement with the Alpha male and his seedy clansmen and women, and folks start getting murdered with the twins always being peripherally involved. Are they killers? Are they insane? You'll have to watch for yourself.
This isn't a horror film, per se, more like a British gaillo or murder mystery, but I found it interesting enough, although a bit dated, as we've been desensitized thru the years since its release. Certainly deserving of a rental, but if you're not a fan of the late 60`s scene, probably a drag, man, a real drag.