During the episode, fans met Emma Knightly (Anastasia Griffith) , a member of the group who Liz had been suspicious of.
After following her it was soon revealed Emma had previously worked with Red and knew Liz’s real identity but agreed to keep quiet and work with her.
However, a fan noticed a huge blunder during a scene with her and fellow thief Jessica Piha (Ito Aghayere).
The observant viewer exposed the blunder on a movie mistakes forum which happened when they were plotting to take the list which was on a chip, embedded in someone’s skin.
source: express.co.uk