"Look around, Clara!" He does a quick twirl as he exits the Tardis and turns to stand, arms open, smile wide, as he waits for her opinion for a fraction of a second before telling her, "Terra-forming's a bit sluggish – that's the bitterness in the air – but it was only created for the tourists. Tourists from all over the galaxy who come to explore the land and visit the Historical Monument to Robotronics Advancement, a museum of the entire history of artificial intelligence throughout the galaxy that holds the largest receivers of all learned information transmitted by participating robotics, creating the most complete encyclopedia of robotic investigation!"

He gapes a moment, waiting for her nod of approval before continuing, wrapping his hands before moving forward with her at his tail, "And then you have the traders. Not always the most pleasant folk, who come to trade scraps and bot parts, and search for the fabled gold hidden away in pockets of this place nicked from those robots made for the wealthiest in the universe…"

His words blend with the clangs of metal on metal around her and the rapid speaking of those on the streets selling books and bits and she smiles politely as someone offers her a sparkling whirring piece of electronics for a form of money she'd never heard of. The ragged man continues walking when he realizes she doesn't truly understand, and her eyes follow him down the darkly paved road lined with steel slabs that reach into the sky and dripped eerily with water.

Clara's eyebrows rise as she looks upwards to the sky – which could easily have been made of sheets of frosted aluminum – and when she looks back, she watches the Doctor stop, glancing at the robots and patrons that make their way past.

"Planet full of shiny things, it's a wonder you don't call this home," she tells him quickly, smirking at the notion that he would be like a child in a toy store in a place like this, but when she glances upon his face, she sees he is no longer amused.

He is conflicted. And she's seen that face many times before. This trip, like so many before, was no longer what it should have been when he flipped the lever on the Tardis to impress her with a planet, or moon. It was a problem to be solved, and obviously the Doctor would be the one to solve it. She readies herself because she's frightened – something she could never admit to him – and when he shifts to look to her, her heart jumps slightly, but she remains constrained for him.

"Something's wrong here," he speaks, but it's to the moon around him.

Clara nods, "Yes, it's full of robots." She feels clever, but he ignores her.

A couple moves past, arms locked, laughing with each other as the Doctor's brow furrows and he continues, "Very happy humans and very sad robots," he gestures to a medium sized downtrodden bot with silver stripes as it slowly makes its way over the sidewalk, one clunky leg shifting after the other around a building.

"Robots can't be sad," Clara tells him, but she gets the impression her knowledge is impeded by the limits of her time. "Robots can't be sad," she repeats curiously, "Can they, Doctor?"

"You thought the Tardis was sick." He shoots her a quick grin then reminds her, "Robots can be anything you program them to be."

But she steels her face in a mirror of his smugness and declares stubbornly as she remembers something that might be foolish, but worth pointing out to at least find out if it's true, "Doctor, robots can't be sad, isn't there a law, or a rule or something, written into their coding? They live to serve others – see serving,"she gestures at a robot asking a human if they're in need of assistance," – they should be satisfied. Happy."

He shakes his moment of pleasure away and waves an arm, "And yet, they're sad. Why are they sad?" The question is pained and pointed as he moves closer to her.

"They're not sad, they're robots!" she responds in an exasperated tone to match his own.

And Clara realizes, when he interrupts with, "Let's ask one!" that her argument has been all but forgotten.

She sighs, knowing it was pointless from the start, as she rushes to follow him towards a larger robot standing facing a wall, an odd sight in itself. They remain a moment, staring at the large metal man and Clara watches him Sonic it up and down, quickly reading something on the silly device before pocketing it.

"Excuse me," the Doctor asserts, "Excuse me, I am in need of assistance."

The robot shifts, its gears turning and working roughly as it takes two steps to turn sideways and another two to face them. "How may I assist you?" The question is weak and Clara stares at the tin man questioningly because the Doctor is right – it seems sad.

"What is your purpose?" He asks, arms folding, one hand already dipping into a pocket to grasp the Sonic Screwdriver deep in his pocket, ready to examine the robot again at the slightest sight of change.

There's a moment of silence as the bot considers the question – to Clara it almost seems lost in confusion – and it explains, "I am a host."

Lifting one hand, open palmed, the Doctor presses for more, "A host of what? For information, to entertain? Explain."

The robot stares at them. "How may I assist you?"

"Answer the question," the Doctor responds, voice low.

Clara raises a hand slightly, both gaining the robot's attention and the Doctor's curiosity. "How may you assist us?" Then she adds, "What is your function?"

Something sparks inside the robot and it watches her before telling her, "I am a guide. Would you like to visit the museum?"

At that moment, a small bronze robot bumps roughly into Clara, sending her into the robot in front of her with a loud bang. Clara pushes off the metal and looks to the smaller robot the Doctor is already scanning as it backs away and does a turn. It seems panicked.

Panicked, Clara tells herself, a robot can't panic. And just as quickly as it had rushed into her, it zips away as the Doctor examines his readings.

"Anything of interest?" Clara questions.

He doesn't answer her, simply turns to the robot and asks quietly, "What is your name?"

"Name?" Clara asks.

The robot says the same.

"What is your designation? Your make? Your model? What are you?" The Doctor clarifies.

"I am one of many, I have no designation, make, or model." He pauses and then asks again, "Would you like to visit the museum?"

The Doctor smiles and answers slowly, "Yes, yes, we would like to visit the museum."

Two more steps and the robot is facing the asphalt and he steps out onto it, leading them. Clara hesitates and the Doctor turns to look at her, a smile on his face, "Well, come along!"

She rushes forward and he offers his arm. When she slips hers through his, he gives her a reassuring squeeze and she feels foolish. Of course she's safe, she's with him! But every heavy step the robot in front of them makes chips at that assurance and as they pass through the streets, towards what looks like a monorail station, she's found that she's back to being just a tiny bit terrified.

Clara glances at the outside of what seems to be the train station – possibly some kind of docking station as she can see ships overhead and sees the commotion of new arrivals – and she notices posters.

They're Missing posters.