4.
Jo flourished her name across the line and tapped the papers together. "There you are! Ready to go."
He nodded. "My thanks for your patience with our bungling. You're off home?"
"I might pop in on the Doctor."
"Don't let him set you to working. You're off duty!" he reminded as he held open the door for her.
"Oh, don't worry about me. If I stay, it'll only be because I want to. Or because he looks helpless." She smiled at the Brigadier's half-formed protest and gave a little wave as he closed the office door. She paused partway down the hall to duck briefly into the loo. If the Doctor did manage to keep her, it could be a while until she had another chance at it.
A little further down the hall, the tall Sergeant reached the top of the stairwell and paused to square his shoulders and check his uniform before stalking reluctantly down to the Brigadier's door.
Benton barely scraped the wood with his knuckles before getting a response. It looked like the Brig was in after all.
--
The Doctor wasn't entirely surprised to see the Brigadier enter the lab. Alistair seemed to often drift his direction when he was trying to avoid paperwork, at least when there weren't other people around to keep him on task such as in the middle of the night. He usually didn't stay long.
"Good evening, Brigadier," he said amiably, barely glancing up from where he was carefully twisting wires together in his hands. He paused to snip off a rough end with the wire-strippers and looked up again, as there'd been no response. "Anything I can do for you?"
The Brigadier was looking at his TARDIS with more interest than he normally gave the blue box and looked back at the Doctor almost nervously, holding his side. "Can't say its been the best of evenings," he said. "One of my own men accidentally let off a firearm."
The Doctor frowned at this. These military men were always gun-happy, in his estimation, but not generally careless. He tipped his head towards the Brigadier's side. "He didn't hit you, did he?"
Lethbridge-Stewart slowly wandered over towards the police-box in the corner, looking down at the tangle of cables that lay across the floor. "Yes," he said briefly. "Been patched up, though. Not to worry."
"The devil!" the Doctor sympathized. "New recruit?"
"No." The Brigadier said, "Sergeant Benton."
"Benton?" the Doctor was honestly startled. "He shot you? That's rather uncharacteristic of him, isn't it?"
"Demmed bad luck, that's all," shrugged the other. "I've had worse I dare say. What's this do?"
The Doctor frowned again, wondering at his unusual interest. "I doubt you'd understand."
"Try me."
"All right. In essence they're a bit like a radio, you could say. Each one's tuned to a different frequency, though it isn't radio waves they're picking up, but recognizable anomalies. When they detect what they're tuned into they record that information, which I can then review. Does that answer your question?"
"Hm," the Brigadier said. "The little black squares, they can detect and identify aliens then?"
The Doctor gave him a sharp look. "Sort of."
"I see. Hm. Detachable?"