It was troubling, the entire thing was a worry for Jack but the ship itself is likely being pulled apart by The Doctor right now. It's the fact his wife and Liz went missing. Owen made note of Liz having never returned and Jack's not happy. The events with Rhys are still fresh in his head and he wasn't about to have another tragedy happen so soon.

Jack was standing at the ledge of the building, it would be terrible if John were to show up and push him off this one. It stood much taller than the ones in Cardiff and it would leave him with more than a bad back. He survey's the people down there and perhaps he could find someone or some clue that would lead him to his missing friends.

"I just need something to get the two of you back." Jack muses, to himself and he looks up to see the stars up above him. Jack's been through places like this one before during his day's in the Agency. He recalls a visit to this ship before but never did he question it's workings. That wasn't until he came across The Doctor and he became a changed man.