Apparently Lake has replaced John Munch (Richard Belzer) as the partner of Fin Tutuola (Ice-T). I don't think Munch appeared this episode. If they're phasing him out, too bad. He's more interesting than Lake, who's the least interesting character on the show (so far).
Beach claims they're working on his character, adding depth to him:
Adam Beach hopes to ratchet up intensity on 'Law and Order: SVU'
"Every week, we build a new life for him. This is going to be a three-year character development for me and I really like that. I like doing things that are connected to me personally," says Beach.
"The challenge is that we are trying to find out who this guy is. There's a little suggestion that he's fast at putting things together. There are other questions; like what's his connection to SVU? Was he a victim? And how? And how are they going to bring in his connection of roots to the city? His family were ironworkers, so he's really embedded into the city. We're finding new things out about Chester all the time."
The teaser for "Impulsive":