The prosthetic right hand is installed to replace Fergus's lost right hand.
The prosthetic limb is Da'at Yichud technology that enables humans to replace lost limbs with cybernetic ones. The technology is still being perfected and is prone to glitches in which causing user to experience Alien Hand Syndrome. A prime example is Fergus's prosthetic right arm which repeatedly smashes a biscuit into his face when he tests it or the fact that the hand is seen abusing and humiliating him frequently. There is a theory that due to the fact that the prosthetic limb is deeply connected to the brain of the user, the limb can act out of a user's personal impulsiveness and inhibition. The largest evidence of this is when Fergus attempts to confess his love for Maria Laurent, but his limb gropes her by the breast, leading Maria to slap him.
Fergus Reid's new prosthetic right arm to replace his original arm.