Jumping in!
Amy had searched the city up and down to find public records on the Welcome Center. There wasn't much-- the building truly was a mystery-- but she was able to track down work orders for independent contractors and safety certificates for the fire escapes, etc. The signatures were nearly illegible, and there was no printed name, but it was better than nothing. She was making her way back to the Welcome Center on foot to show Tonks what she'd found when something in an alleyway caught her eye.
Was it...? Could it be...? The TARDIS stood, big, blue, and impossible as ever, tucked neatly against the wall of the alley. Rushing toward it, Amy pulled her key from her pocket and made to turn the lock with shaking hands. One single word echoed in her mind. Rory. Rory. Rory.
She didn't need her key after all, as the door was already unlocked. She rushed inside, fully expecting to see the Doctor at the controls, a smug grin on his face because he'd managed to recover the TARDIS he somehow misplaced so many weeks ago.
"Doctor! You found it! Where's Ro--"
She cut off suddenly when she realized that this looked nothing like the TARDIS she knew. Neither the Doctor nor her husband were anywhere in sight. Instead she saw a man with spiky hair and a suit who looked to be in incredible pain, and standing next to him...
"Donna? Is that you? What's going on, where's the Doctor? Or is that...?" Getting closer to the center column, Amy recognized the pale blue shirt and brown tie with a swirl pattern that the man was wearing. She'd seen them before, when she first met the Doctor that night in her aunt's garden. Could this be the Doctor Donna knew? The one that came before her own?