Takes place after "Captain Jack Harkness".
There should be an upside to no longer sleeping, but if there is Jack can't seem to find it. Even his nightmares have learned to chase him into the waking world. He can't shake the sorrow of leaving 1941, the look in the real Jack's eyes when he walked away. Around him the empty Hub echoes with the soft hiss of falling water and the deeper whuff-whuff of the pterodactyl breathing. This is the time the horror rushes back and solitude is its invitation.
Riding back in the SUV was the first flash of fear. He is a dead man wearing a stolen name. Worse, he stole history. The record changes that made him "Captain Jack Harkness" deleted from history the story of a real man's final heroic death. He's made some small restitution in telling Tosh what happened to the Captain but confronting the real man has forced him to admit that he's a murderer. He'll spend all of eternity chained to the memory of a good man who vanished to give his name away.
After the team leaves he traces the pattern of a crystal glass and starts to wonder how much of it is his fault. Would Capt. Harkness have died without the knowledge he had seen in these blue eyes? Did the goodbye kiss make one of those young pilots doubt their commander? If he'd never stepped into 1941 would Capt. Harkness still be alive? With all his years of crossing time cause and effect blend until one can't be separate from the other.
From one perspective, it couldn't be his fault. He first set foot in 1941 after Captain Harkness was dead, stole his identity, and joined the Doctor. Joining the Doctor takes him to the future, where he cheats death and goes back to the past. He should have been nothing more than a silent witness to events but he couldn't leave well enough alone. Now he knows that he was there before, changing the Captain's actions, making his death more likely if not outright causing it. He's lived through the 1940's before and knows how homosexuals are treated and still he kissed that man publicly.
He's reaching for the phone before any one thought is clear in his mind. Ianto's voice sounds calm over the line; barely a trace of disturbance when his greeting is met with only silence. He can't choke out words, everything trapped behind a wall of guilt. The crystal slips through his shaking hand and shatters on the floor and hearing the crash Ianto knows where he's needed.
"I'm on my way, sir." Then the soft click of disconnection.