Torchwood 2x12 - "Fragments"
 

"Fragments" by Chris Chibnall
After the team gets signs of an unidentified life form, they go to investigate. Searching an abandoned building, the team discover it is a trap and the building is bombed. The resulting explosion causes the team to be trapped under piles of concrete rubble, where their lives flash before their eyes revealing how each member got recruited to Torchwood.