"I've found, over the years, that the Doctor is usually right," Sarah Jane said. "He's just insufferable once he realizes it himself." She offered a cheeky grin so Sam would know she was joking. "We'd need to do a lot of comparing to figure out the pattern, if we can," she continued. "If it's some sort of aliens that have us captive, the thought process might not make sense to us. We might not have the ability to see the pattern." The Doctor would be able to see it, Sarah assumed, if he could consider all the facts together. Time Lord brain, and all.
"That's the spirit," Sarah said, squeezing his arm before letting it go. She reached into her pocket, pulling out the bits of Mister Smith's buttons and the little antenna that belonged to K9's ear. "I know it doesn't look like much of anything," she said, glancing up at Sam. "But this? If it's genuine, this is a piece of my dog," she said, pointing to the antenna with her other hand. "And these are off my computer. Both of which are in my house, with my son." She sighed. "As upsetting as they are, at least it's nothing of Luke's. That makes me think he's safe." Probably. As she was fretting to the Doctor before, though, if their captors could get in and take these, then what was to stop them going back and taking something of Luke's, or Luke himself? She could only hope that the boy wasn't home, that he was with Maria or Clyde and their families. That would keep him safe, wouldn't it?