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Anna Maxwell Martin, Rachael Stirling, Julie Graham and Sophie Rundle in The Bletchley Circle
Alice (Hattie Morahan) has now been convicted and is facing the gallows. It becomes a race against time to prove her innocence and to save her life.
The girls need evidence and they quickly start the search with the documents found at Lizzie’s (Faye Marsay) flat. With a search through the records, help from Lucy’s inside police info as well as Alice’s knowledge of Richards background the clues lead them to Porton Down.
They believe that Richards was killed as part of a wider Military cover up and that Lizzie, by association, is also being set up by the same people and framed for his murder. It turns out the military hospital where the men who were injured in the chemical spillage is the same hospital Timothy (Mark Dexter) was treated at when injured in the war – they see a way in – Susan (Anna Maxwell Martin).
In the meantime Susan has been grappling with her own issues after her experience with Crowley and because she is again having to keep secrets from Timothy. She is scared and reluctant to get involved but sees that it has to be her and that this could be their only way to save Alice.
Whilst Susan heads to the hospital the others track down Professor Masters (Paul Ritter), a name that has popped up as the connection between Richards and Porton Down – he may be able to help.
When they arrive at his London house, Masters pulls a gun on them – he believes them to be spies as he did both Richards and Lizzie, which is why he killed Richards and framed Lizzie.
After gaining access to the hospital and a bit of sneaking about Susan comes across a badly injured soldier who tells her the truth behind the chemical experiments at Porton Down and how he and others were lied to by their own military and used as lab rats.
Susan is caught and arrested by military police and Timothy is called. She realises the level of trouble she is and that there is no way out – she is forced to tell Timothy everything including her history at Bletchley Park that she has kept from him all this time. In doing so she is breaking the Official Secrets Act. As soon as Susan mentions Masters name the Colonel (Tim Piggott-Smith) realises how far things have gone and he sends the Military Police to save the girls in the knick of time. It is only as he is arrested that Masters realised how wrong he was.