Ace hears the engines first; by the time she gets outside, the TARDIS has fully materialized.
"Professor!" She's got so much to tell him, she can hardly wait.
But when the door opens, it's not him. Instead, some swishy-looking bloke with long hair and a longer coat steps out. He looks at her vaguely, as if he's trying to remember where he's seen her before.
"Professor?" she calls again, trying to look over the stranger's shoulder. She darts past him and into the TARDIS, hoping against hope that he'll be there.
But in her heart, she already knows he's gone.