There is some good philosophical sci-fi in this one, but they spend two episodes skirting round the edges of the idea, never really probing deeply.

Its a shame that the Gangers go loopy-crazy, because it undermines the idea that you have two creatures who are equally human who have been created in different ways. It would be easier to empathise with the Gangers if you didn't see them turn into a malevolent snake, or run down a corridor screaming with their mouth's wide open (which was giving me The Lazarus Experiment flashbacks). At some points Matthew Graham was going to efforts to make them actively evil, more so than the human's opposite them.

The child on the avatar space phone call was used to ram the point home that its a struggle for two people to share the same history. I think they pushed the emotion too far, it felt forced and ineffective. Also the child was left on the line saying "where's my daddy" for what must have been 3 hours. I doubt any kid is hanging on that long on their birthday - regardless of who is on the other end of the line.

I don't know how I feel about The Doctor snapping his fingers and getting rid of a blood clot, feels disrespectful for audience members who have these problems in real life. Feel equally odd about him killing Ganger Amy after a story which seems to otherwise resolve itself by saying how we should be treating the Gangers humanely, and with parity to humans.

Why was Matthew Graham given a second crack at Doctor Who given his work on Fear Her. There was a data point which was ignored here. Very few writers have been given this chance, why are we double checking the skills of writers who we know struggled with previous contributions?