Summary: Donna and the Doctor have a disaster to prevent.
They were flying along, minding their own business, heading for the Flishpin Nebula, when the TARDIS suddenly lurched, turned upside down, flipped right-side up, changed direction, spun around several times, and finally settled into more or less stable flight again.
Donna clung to a coral strut, unwilling to let go.
“What the bleedin’ heck was that?”
Picking himself up off the floor, the Doctor approached the console.
“Rogue comet,” he explained. “Almost hit us. Oh, not good! It’s headed for an inhabited planet!”
“What can we do?”
The Doctor grinned. “Lasso it and change its course!”