Jeremy Jordan will appear in an October installment as Joey Castoro, the son of the surgical patient who died in Watson’s care. The surgeon-turned-P.I. has an affinity for Joey, but her affections for him are tested when he comes to her with an unexpected request.
"We’re going to… explore Joan’s feelings of guilt," executive producer Rob Doherty recently told TVLine. “At what point do you tap your guilt and give yourself permission to live a life?"
Lynn Collins will guest in the episode as a brilliant and beguiling math professor who helps Sherlock and Joan with the investigation of two murdered mathematicians.