The only "dud"of series 4 in my opinion. Kinda a generic villain and plot compared to the rest of the season. Nice to see Luke and K-9 again, though.

It’s a story that we’ve seen many times before, the possession of a protagonist while their life force is sapped away - think Midnight. But it’s done well, the villain is a good match for Sarah Jane and with Luke and K9 appearing there’s a strong “end of term” energy to it.