the necklace and some dead ends

When the guy breaks into Clive Bonn's home to attempt to kill him, the guy defended himself and stabbed him with a scissor in the shoulder blade. He used the bag ties and bag and tape. He was copying Peter.

And when Marcella demands to see Henry's shoulder we see the bite mark but no stab wound. So that proves it wasn't him. At the end of one of the episodes there is a clear shot of a red haired man looking into a mirror with an injury on his shoulder blade.

Meanwhile the weird chubby girl who cam-whores and sleeps with married men to steal their jewelry had Grace's necklace and gave it to her friend as a gift.

She stole that from some married man but Henry clearly stole it from Grace during his copy-cat murder. So, did Henry actually kill her too. And why bother? he didn't use the same means of murder. It was vehicular homicide so that made it seem much less like Peter and it couldn't of been his gay best friend because he doesn't sleep with women and he's not married. Also, I thought Henry was meant to be gay too although it's not conclusive, but that was my take on it.

It really proved there is a third killer and yet Henry orchestrated everything?

Can someone explain this to me? The body moving brain fart was bad enough.