4 stars for a very clever story, with drawbacks. I followed what was going on, and who was who, and when was when, until about halfway through. The multiplicity of characters and time jumps lost me, but I stuck it out because I had to get to the resolution.

Spoilers (BIG spoilers) and questions:

-While "Aiden" was inhabiting another host person's body, was each other host acting as themselves, or as another "Aiden"?
-Given that Blackheath was a prison, who actually were all those other people (aside from Aiden, Anna, and the Plague Doctor) - other prisoners? Conjured (AI?) characters?
-The reason why Aiden was in his predicament requires a LOT of suspension of disbelief. The Plague Doctor, who was operating under orders from his superiors, was actually ridiculous.
-There were too many characters whose names started with the letter D. I started to think that was a clue.