Bit of a pointless runaround, but great in terms of the TARDIS crew.

The Doctor is presented as a fun detective, and can't wait to solve the mystery of the deaths. He takes command easily (a bit too easily) and as he delves further into the Moray Rose's investigation, it leads us into a very compelling story. However, this was let down by what happened to Leela in Part 2, as that took precedence and meant that the investigation became the side plot, when it was easily the far more interesting of the two. Not to say that Leela hunting the Doctor wasn't captivating, but it wasn't executed very well, even with Louise Jameson being a star as ever. Despite this, the conversation between the Doctor and Leela near the end was very sweet, and you can tell that the pair are starting to make up.

I don't think Big Finish understand this Master well enough to write stories about him. This incarnation of the Master is meant to be dying and crispy, not up and about, disguising himself as inspectors. However, I do like that he gets other people to do his dirty work for him, such as Leela.
The Salonu are generic bug-eyed monsters (no pun intended) and it's shame, because they were set up well in the first part, but again were overshadowed by Leela's hunt.

Calvert was a developed character and there was some great moments between him, and I'm surprised he died so soon - and in such a disturbing way!

To conclude, it's not the best, and I hope the Master doesn't return for a while - it hasn't been long since the Oseidon Adventure and I don't want him done to death.