The Doctor didn't even bother with David. With the exit gates open and the threat of losing his only catch, he turned and followed Ace with an inhuman fixation that was terrifying to witness. It was as though taking Ace's life was the most important task he'd ever undertaken. Meanwhile, Ace's borrowed time was up. Meg was leading him to the exit gate where Claudette was waiting for everyone, but the Doctor started gaining ground on them, and fast. Fortunately, so did David.
David pumped his legs as hard as he could until his chest began to burn, then kept running because he still wasn't close enough. Putting himself between that psycho and his family was the only thing that mattered. When he saw the Doctor rearing back to swing that spiked stick, he had no choice but to dig deep and perform a powerful dead hard lunge straight into the Doctor's path. David felt something cold and hard rake across his back, and the next thing he knew he was face down in the mud. As he lay there, his flashlight just out of reach beside him, he grinned with satisfaction.
The Doctor reappeared less than a minute later, and Ace wasn't slumped over his shoulder. He and the others must have gotten away. David chuckled mirthfully as the Doctor reached down and picked him up with relative ease.
Fight ain't over yet, Doc.
David went absolutely ape shit trying to wriggle out of his captor's grasp, and they both wobbled back and forth on the uneven terrain. That was when he heard screaming all around them. It took a moment to realize it was the others, coming back to save him from the Beast of the Fog they seemed to fear the most. They were scared, and David thought he heard one or two of them crying, but they were here. For better or worse, his family had his back.
As the Doctor slowly carried him past a row of barrels, Meg suddenly popped up a few meters ahead of them and grabbed hold of a heavy wooden pallet with both hands. The Doctor tried to take her head off with the stick, but she was just out of reach. With nearly pitch perfect timing, she used all of her strength to slam the pallet down right on top of him, causing him to drop David, who landed on both feet and hit the ground running.
Meg then used the time the Doctor spent destroying the pallet to go around the barrels and race past him. When he turned around, Claudette was there with a flashlight of her own. David felt so incredibly proud of them, and was truly honored to call them his family. Ace waved everyone over as they approached the exit gate, allowing each of them to pass through before escaping himself. All in all, the Entity was displeased.
The Doctor had failed.