Hmmm, good point. I was sorta thinking that Jekyll and Hyde are dealt with in “Strange Case” (episode 4)
Hank Harris and Sam Witwer haven’t been spotted on set in a while, either. Last I heard of them was when they were reportedly doing some re-shoots at the end of August, which was also when 605 was being filmed. So yeah, I think 604 will likely be Jekyll and Hyde’s curtain call.