13. "Gridlock" - The Doctor brings Martha to New New York. What do they discover in the 'Fast Lane' of the Motorway?
From Quiz "Doctor Who" - Series 3
Answer:
The Macra
Taking Martha on another trip, this time into the distant future, the Doctor ends up bringing her to one of the places he brought Rose, New New York on New Earth. When he arrives this time, however, it's in the slums, and Martha is promptly whisked away by two people who plan to bring her with them into the carpool 'Fast Lane' of the New New York Motorway, one which has trapped drivers for decades without letting them out. When the Doctor follows he discovers that feral, enlarged Macra, crab-like creatures, devour people in their vehicles at the bottom of the Motorway, and the only way he can inevitably save Martha (and the rest of New New York) is with the help of the Face of Boe, who's dying up in the now-empty senate on the surface. Fortunately, the Doctor and the Face of Boe are able to do so, though at the cost of the latter's life. Following this, Martha is able to get the Doctor to open up a bit about his past.