Doctor Who: 10 Times The Doctor Lost
5. When He Was Forced To Watch River Kill Herself
One of the most notable additions to Who canon since the show came back in 2005, Professor River Song was first introduced in the Series Four two-parter Silence In The Library/Forest Of The Dead.
But instead of being another throwaway side character on one of the Doctor's adventures, River was positioned as someone who shared a deep personal connection with him. The wrinkle here though - because of some wibbly-wobbly timelines - was that the Doctor hadn't actually met her yet.
Throughout both episodes, we learn a little more about the Doctor and River's other adventures, documented in her TARDIS-blue diary (spoilers!), and it quickly becomes apparent that she's crazy in love with him. And at the end of Forest Of The Dead, we get to see just how far she'd go for her beloved Time Lord.
While preparing to sacrifice himself by hooking his noggin up to a computer terminal, the Doctor is knocked unconscious by River, who takes his place. After a brief countdown and an emotional farewell, River is killed, with the Doctor forced to watch on, helpless, having been handcuffed to a nearby metal post.
While the Doctor can't fully understand what he's lost at this stage (all of his adventures with River are still to come), he can't exactly put her death behind him, because he's reminded of it every single time he sees her from this point onward. Carrying that baggage must hurt like hell, but all the Doctor can do is grin and bear it.