That went by so incredibly quickly. Reminded me of why I loved PJ Hammond's Sapphire and Steel so much. Dark, eerie and nobody won in the end. All Torchwood did was stop the deaths for a while.
Jack flashbacks! Jackbacks! So, exactly how long has Jack been stuck on earth in this time period? Assuming he doesn't age as a side effect of the not dying, has he been there since at least 1909? Or were 1909 and his meeting with Estelle during the time he was a Time Agent?
Some very nice touches in the timing of stuff - a couple of points I jumped at, like when the telephone rang.
Creepy little girl. Very creepy little girl. Towards the end, when she was actually finally talking, she was sounding like a serial killer.
So, realistically... what else could Jack do at the end? Keep her there, and the deaths would continue. Kill her, and what happened to his troops in 1909 would probably happen to the Torchwood team. He himself might have risked it, but after they went after Estelle for no particular reason, I don't think he could take the chance.
Would have liked to see more from Tosh and Owen. Ianto did have the interesting scene with Jack at the beginning at least. I can hear the word processors of countless Jack/Ianto slashers firing up right now... assuming they're not constantly rewinding to watch shirtless!Jack again and again.