The sonic screwdriver can open anything. Almost.
She could hear the clack of huge claws, hear the scrape of massive chitinous plates against the corridor walls as the monster squeezed around the corner behind her. The Doctor sprinted ahead of her, the sonic screwdriver held out before him as they barrelled down the corridor to the door.
Donna looked back over her shoulder, dread gripped her insides as the lights behind popped, crushed by the giant size of the monster inexorably squeezing its way toward them. She slammed to an abrupt halt and bounced back, briefly squashing the Doctor between her and the unopened door.
He kept yanking at the door knob, jiggering at the keyhole with a paperclip.
"Hurry up!" she yelled. "Sonic it!"
"Then what's the problem?"
"It wasn't locked."