It had been little things throughout the day that got Jo down. She didn't normally brood and ask herself serious questions about who she was, but three different people had made comments that made Jo wonder about what she was doing…

The first time had been when she was talking on the phone with an old friend from school. She and Kelly had been catching up, finding out where life had taken each of them.

"So you got that posh job your dad promised, right?" Kelly asked. "It was some international gig, wasn't it?"

"Yeah, UNIT," Jo reminded her. "I'm working there now, as a civilian of course."

"Is it good?"

"Yeah, I really enjoy it. They've got me working with this scientist guy called the Doctor who is really clever and it's a lot of fun."

"The Doctor?" Kelly laughed. "What is that? Some kind of code name?"

"No, that's just what he calls himself," Jo said. She always thought it was a little strange too, but it didn't bother her.

"That's kinda funny you ended up working with a Doctor," Kelly said. "I always thought you hated science."

"Oh, it's not so bad," Jo said, thinking that it was really spectacular. "I don't actually have to do the experiments myself."

"Yeah, that's probably a good thing," Kelly giggled. "Remember how you were always breaking things and knocking over the beakers in Professor King's class?"

They both laughed and Jo sighed into the phone. "Yeah, I still do that occasionally. But mostly the Doctor has me handing him stuff and doing the calculations. I'm actually really good with the figures."

"Sounds better than being a temp," Kelly said enviously. "Though you're kind of an assistant too, if you think about it. I don't like doing all the paperwork in the office, but at least I'll eventually have the recommendations to start a decent career. I wouldn't want to spend my whole life as an assistant to some Doctor in a lab all my life."

"Yeah, me either," Jo said. She listened to Kelly laugh on the other end of the line but felt no joy. She wasn't sure why, but the idea of having any job that took her away from the Doctor's side made her a little sad. She should have been eager to move on, shouldn't she?

The second time was when someone said at lunch in UNIT London headquarters. She had spent the morning in a briefing with all of the other members on her task force and there was a break for lunch.

"Jo, I wanted to ask you what your opinion was of that presentation," the Doctor said, coming along beside her. "What did you think of the way the agents went about finding out information?"

She told him her opinion on the subject as they walked to the cafeteria. He agreed with her, for the most part. She followed him into the cafeteria and stood in line with a tray to receive lunch.

"There's that chap I was telling you about," she heard someone say behind her. She glanced over her shoulder and saw it was two young men who were also in the employ of UNIT.

"He's the Doctor," the man continued. "Strange old fellow. He's always running around when there's trouble. Brigadier keeps him on because he's so clever and knows things that nobody else seems to know."

Jo smiled at the strange form of praise he gave the Doctor. She kept going through the line slowly, still listening.

"Who's that pretty girl with him?" the other man asked. She assumed they were talking about her.

"Oh, I have no idea. His assistant or something, I think. Bit of a ditz."

Jo didn't listen to the rest. She felt small and unimportant. Everyone knew who the Doctor was. She was just his stupid, useless assistant. But she reminded herself that those were just strangers. People who knew her well would know that she was much more than that.

Then she talked to Sergeant Benson. He would never purposely hurt her, but he was thoughtlessly talking to her and she took it as the confirmation of her fears.

"Has it been a long day for you too?" Benson asked her. They had both taken an afternoon break at the same time and ended up sitting in the snack room together.

"Oh, you would not believe the day I've had," she sighed and closed her eyes. "It feels great to sit down and put my feet up."

"I know what you mean," Benson said. "I'm looking forward to taking leave for Christmas. The rest of my family keeps pressuring me to come out to stay in the country with them for a while, so I've finally committed."

"You're lucky," said Jo. "At least you get a break. I don't even know if the Doctor celebrates Christmas. He might not give me the night off and I'll end up like poor Bob Cratchit."

They laughed and Benson stood up, stretching his tall form. He poured the last of his drink down the sink.

"Well, it won't be this way forever. One of these days you'll find another job and the Doctor will have to find some other companion to run around with." He went to the door and smiled at her. "Anyway, I need to get back to work. Nice talking with you, Jo."

"You too, Sergeant," she said, waving. He left the room and she sat there, alone, thinking. Then she stood up and went to find the Doctor.

He was in his laboratory, a pair of protective glasses perched on his long nose and a pair of white gloves covering his hands and wrists. He bent over a bubbling concoction in a beaker and slowly began to add a tiny vial of bright blue liquid to it.

"Doctor," Jo said as she stood next to the table, watching him work.

"Hmm?" He asked without looking up, preoccupied with his work.

"I was just wondering," she paused and wondered how to say it. "That is, I was thinking, am I very important to you?"

The Doctor looked over at her as he continued to pour the liquid. "Of course." He smiled and turned back to his work.

"I mean am I valuable to your work? Like, do I really help you and do you need me around? Or are you just keeping me around for some other reason."

The Doctor finished what he was doing and stood up to face her.

"What other reason would that be?" he asked.

"I don't know," Jo shrugged. "Maybe because I'm young? Or because I make you look good? Some people think I'm just your pretty assistant and I thought it might be true."

"Jo," the Doctor said very seriously, "You are and always will be very important to me. I wouldn't have asked you to help me if I didn't need your help. I picked you because you're just right. You aren't annoyingly clever, or constantly busy and troublsome. You do what I tell you, but you're also wise so I can trust you to make the right decisions when I'm not around."

Jo tried very hard to listen to everything he was telling her, but she couldn't help noticing that his concoction was bubbling and rising quickly.

"Doctor," she cried, pointing to the glass as it overflowed.

"Oh no, quick!" The Doctor gathered up his other beakers and experiments, trying to keep them from harm. Jo had the sense to grab a lab suit off of the back of the door and ball it up. She threw it onto the chemical solution that was flowing across the table and it soaked the liquid up before it could damage anything. Both she and the Doctor sighed in relief.

"And, of course, I need you to make sure I don't blow up the entire UNIT headquarters," the Doctor said, smiling at her. Jo laughed and hugged him.