After dinner, the Doctor gathered a few supplies from Artie's makeshift lab and they set off in search of the mystery bugs.
"So, there are really tiny little aliens the size of bugs?" Angie demanded. "And they fly around in spaceships?"
"Yes, there are, and yes, they do," the Doctor replied with infuriating calmness. "You just have to keep your eyes open, and notice what's going on around you. I had an adventure with an Isolus during the last Olympics. Tiny thing, the size of a luna moth, and it made an entire stadium full of people disappear. Well, it did until Ro - er, my friend and I, got them all back again."
"The news said that was just a publicity stunt. Special effects," Artie said, slightly confused.
The Doctor whirled suddenly and tapped Artie on the nose with his index finger. "The news says a lot of things, Artie, but I think by now you've seen a thing or two yourself. You want to learn to trust your own senses and make your own conclusions. That's what science is all about!"
"So, if that Isolus thing was a little alien, how'd it get here?" Angie demanded.
"In a little spaceship, about the size of a gull's egg."
"What happened to it?" Artie asked.
"My friend and I, we found its pod and sent it on its way back to space."
"And you didn't…I dunno…punish it, or anything?" Angie wanted to know.
"No! Of course not! It was just a child that got lost and wanted to go home. How could I punish someone for that?"
"Maybe your friend could help us," Artie suggested innocently. "The one who helped you with the Isolus?"
The Doctor went utterly still, and Clara saw a flash of unbearable pain cross his features.
"I'm afraid that's…not possible," he answered slowly.
"So," Clara interjected into the awful silence that followed, "you were saying that there are also outer space insects?"
The Doctor flashed her a grateful look, then cleared his throat roughly. "Right you are. Remember a couple of years back, when all the bees were disappearing? Well, some of the bees, at any rate?"
Clara nodded encouragingly.
"Those were Migrant Bees from Melissa Majoria, and they sensed that something terrible was about to happen to the Earth, so they headed home."
"I remember that," Clara said softly.
"So do I," the Doctor replied, with an echo of old pain in his voice.
Clara reached out and took his hand, and they followed after the kids.