10 Darkest Doctor Who Moments
3. Gas Mask Transformation (The Empty Child)
You knew this was coming. It may not be the darkest moment on this list, but it's undoubtedly the most iconic.
The entire scene with Christopher Eccleston's Ninth Doctor and Richard Wilson's Dr Constantine is crafted with incredible intrigue and tension, thanks to Steven Moffat's writing and Murray Gold's unsettling score.
Constantine's coughing and spluttering makes you sense something bad is about to happen, and as the Doctor's examination of the gas mask-wearing patients draws the same impossible conclusion – that they've all got the same injuries, right down to the scarring on the back of their hands – the camera cuts to Constantine's own hand, which bears the exact same mark.
His coughing intensifies and before long, he utters those four famous words: "Are... you... my... mummy?" The Doctor can only look on, helpless to intervene, as Constantine's face morphs into a gas mask.
We all needed our mummies after witnessing that.
This scene was originally even darker too, with producer Phil Collinson noting that the sound of Constantine's skull cracking was edited from the final broadcast. Probably the right decision – it's not like it needed to be more scary, let's be honest.