Detritus took his promise to Ruby quite seriously and brought her a beautiful rock each day. Ruby loved them but Detritus always felt they were inadequate. The city of Ankh-Morpork was built on loam and the remains of its ancient ruins. The only rocks were used to build houses and walls. All stones had to be imported or recycled. So in order to find better rocks for Ruby, Detritus decided to take on some of the watch's body guard assignments. He would escort important people to other cities and keep them safe from bandits or in some cases assassins. All and all, it was a pretty good gig.
At one point, Detritus took over the task of safely bringing a wealthy merchant to distant Borogravia.
No one really lived in Borogravia. It was just a stop on the road to more important places, but the largest sturdiest bridge over the Smarl River was in rimward Borogravia so it had gained popularity with merchants transporting heavy loads. The whole country was very traditional so there was inevitably a troll living under the Pyrites Bridge. Her name was Jade and she owned it.
She also had two growing pebbles. As soon as Detritus crossed into Borogravia, Tuff and Talc were on him.
"Hey, you're a policeman, right?" Tuff asked. It sounded almost like an accusation.
Detritus smiled. He liked children, but never really felt comfortable around them. He was used to hitting things that he didn't understand, but even trolls have morals. Pebbles were soft for the first decade or so of their lives. It was an unwritten troll law that you couldn't hit them until their rock bodies had hardened completely. The conflicting instincts always made his head hurt.
"Of course he's a policeman," said Talc. 'Look, he's got a badge."
"Could be fake, I'm gonna need to see some ID," Tuff ordered.
"You can't say that to the watch! You'll get arrested!"
"I don't have any ID other than my badge," said Detritus not sure what was going on.
He looks a bit shifty to me," Tuff whispered to Talc. "I say we interrogate him. He could be a spy."
"But there's no war," Talc whispered back. "You can't have spies without a war."
Detritus was getting more and more uneasy by the minute.
"What's your name, spy?" Tuff pointed a finger at him with angry suspicion.
"Sergeant Detritus." He had to hold back a sudden reflex to salute.
"See, he's got two names. That proves it," Tuff whispered conspiratorially to Talc.
"You idiot! Sargent means he's an officer! That's something bad!"
"How do you know?" accused Tuff.
"Because, um, the guard on the bridge told me," said Talc hesitantly.
"That guard is a dwarf. You can't trust dwarfs. He probably lied to you to get you scared."
Detritus was going to argue that point but it was most likely true.
"Hey Detritus," said Tuff, "Check this out. I swiped it from a dwarf mine!" Tuff waved a black rock in the air.
"You liar!" said Talc. "You got that out behind the stables."
"No, I swear! I went right up to a mine shaft and nicked it. It's got gold in it no doubt."
"It doesn't even smell like dwarves!"
"Well, I didn't say that it was an active dwarf mine."
"Wait, is that a black glass stone you have?" asked Detritus. He tried to catch Tuff's flailing arm so he could get a better look at it.
"Yeah, what's it to you?" asked Talc snatching it out of his brother's hands.
"Um, I'll trade you for it." Detritus wished he had brought some money.
"All right, I'm listening. Hey give that back!"
"It was mine to start with!" shouted Tuff. He held the rock out of Talc's reach.
"You weren't gonna do anything with it," said Talc.
"I was too! I was going to do a biz-ness tran-sack-shun with Detritus. You're too little to know how to do it."
Detritus watched the two young trolls argue in the same roundabout way of children everywhere. He chuckled when they started to fight each other with stony fists still too soft to do any damage.
"Oh, no," said Detritus in mock dismay, "Now I can't tell who's rock it is. I'll have to find two things to trade for it." Detritus pulled the boys apart. "I'll go get you each a rock from a real dwarf."
Tuff and Talc looked at Detritus in awe. He walked straight up to the dwarf border guard on the far end of the bridge. The luckless dwarf desperately tried to act busy as he approached. It didn't work.
"Constable, see that loose stone? That's no good. Someone could trip on that. We don't want any accidents right? Now pick up that stone."
"Yes sir."
"And uh, that one too."
"Yes sir."
"I watchman's job is to keep the streets safe to walk on."
"Yes sir…"
"Okay then, good job. Gimmie those rocks."
"Er, yes sir?"
"Thanks."
"… Don't mention it?"
Detritus hustled back to Tuff and Talc with the cobbles.
"There you go. Two genuine dwarf rocks I got from a real dwarf."
The young trolls grabbed the stones. Their little eyes sparkled and the black rock was immediately forgotten.
"You two stop bothering the sergeant. He has more important things to do than to put up with you." Jade had exited a nearby shop and walked up to collect her children.
"Oh, they're fine really," said Detritus.
"Thanks for being understanding. They just don't have any respect," Jade frowned and crossed her arms. "Now we're going home and no more runnin' off, you too Tuff."
Detritus picked up the discarded black stone and watched the children walk away with their mother. It made his heart ache.
Next, Detritus took a mission to escort a dignitary to the border to Lancre where a different set of guards would take over. It was a long journey but the cool air did wonders for his brain. All trolls think better in cold environments. It's just part of being a troll. Detritus had seen hundreds of beautiful rocks on the way there but he only ever picked them up on the way back. It was a professional courtesy not to get dirt on a rich man's carriage.
Usually the destination didn't matter much to Detritus, but this time he would be seeing a good friend.
"Bauxite, I got you're black glass stone. Sorry it took so long."
Two border control trolls had stopped the procession. One of them stepped away from the front carriage and trudged through the snow towards Detritus. He looked at the stone with childlike glee.
"You're sorry? Don't be stupid. That thing's amazing! I didn't really expect anyone to remember let alone bring me one."
"You're a good officer. You deserve it. The boys miss you."
Bauxite started checking the closest carriage as he talked.
"I know, but this is where I'm stationed right now," he said. "I can transfer back at the end of the year. Where did you get this stone anyway?"
"Yeah, it was kind of hard but I found a troll rimwards of Borogravia who had one and I traded for it."
"Oh damn, I didn't want anyone to have to go that far. Now I feel like silt."
Bauxite scrawled his name on the bottom of his official checklist and moved on to the carriage at the end of the line. The troll at the front glared at them.
"It was just a little trade." Detritus said.
"A little trade? Borogravia's a stone's throw from Uberwald! That place is nasty. I have to pay you back somehow. I've got half a dollar."
"What? No, I can't do that. It's just a rock."
Bauxite hit Detritus on the head jovially. "It is not just a rock! I've been looking for one of these for years. My girl will be so happy. I was thinking of proposing to her and now I've got the rock to do it! This is perfect!"
Bauxite leaned against the carriage and examined the stone closely. He gave it a cursory lick. Detritus shrugged his shoulders.
"You have to make sure you do it right," he said. "I really messed up with Ruby."
"Is it true she makes you hit her with a new rock each day? That's harsh. You must have blown it big time for that."
"What? How did you find that out? Wait a sec, Ruby isn't harsh! She's a lady and deserves the best."
"If you say so, mate. Here, when you come back next month to escort the dignitary back, I'll have some rocks for you to show your girl. There are some really good ones downriver. I can get Big Jim Beef to help me out."
Detritus glanced at the troll stomping towards them angrily.
"Don't count on it."
Commander Vimes called Detritus into his office. He had been trying to get through some paperwork and was in a bad mood. Then again Commander Vimes was always in a bad mood. It had gotten worse since the Patrician promoted him. Promotions meant more responsibilities. More responsibilities meant more paperwork.
"Maybe you can tell me why you are suddenly so eager to go on escort missions, Detritus. You've been spending a lot of time outside of the city lately," said Vimes.
Detritus stood perfectly still. It wasn't a hard thing to do when you're made of stone.
"I've done all the body guard assignments just fine. None of my people died. I would have known because of them looking dead and all."
"I'm not questioning your abilities. You completed all the jobs and that's great. What I want to know is why you're making such a point of going to other cities."
"Because um, there aren't any rocks here," said Detritus uncomfortably.
"You don't say." Vimes narrowed his eyes at but kept a blank face. Detritus tried to break the silence.
"I need to go other places to get rocks," he said.
"That's either the dumbest lie I've ever heard or it's the most well executed lie I've ever heard. Someone put you up to this didn't they?"
"Yes…"
"Why?" Vimes asked sharply. It had been a long day and it was only going to get longer.
Detritus couldn't lie to his Commander but he still wanted his promise to mostly stay between him and Ruby. It was a troll matter. It just felt wrong to tell a non troll about it.
"It's kind of personal," he said.
"Sounds like blackmail," said Vimes flatly.
"No it's not like that, I swear!"
"Sure it's not. Are you dropping things off or are you picking them up?"
"I pick up only the best rocks sir," said Detritus with pride.
"Quality control?"
"Um… I guess so."
"So what are you smuggling? Slab?"
"No! I wouldn't give that sort of thing to her!"
"Her?" Vimes paused a few seconds to rearrange his thoughts. "This has something to do with Ruby, doesn't it?"
"Yeah but I still don't think they're good enough…"
"Wait a second, back it up. Someone told me you were drug trafficking."
"I wouldn't do that! That's rationally illegal."
"Then what the hell are you moving around rocks for?"
Commander Vimes stared at Detritus with the irritable expression of a man who hates the world and everyone in it. It was the kind of look that said, 'When I inevitably snap, you are the first person I'm going to kill.'
"Well, you see, I have to give one to Ruby each day," said Detritus softly.
"Are you telling me that's trolls have rock collections? That makes less sense than those freaks who put pins in delicate little books."
"It's not really a collection. It's a promise." Detritus looked at the floor.
"It's part of your vows?" guessed Vimes.
Detritus blushed with his chin to his chest. Vimes rubbed his forehead.
"None of my other men have this problem."
"That's because they're not as cultured as Ruby is. She told me—"
"Stop, just stop. I really shouldn't be listening to this. Since now I have lived my life blissfully unaware of troll romance and I wish it to stay that way. As long as you're not doing anything that is or should be illegal, I'm fine with that. I'll tell Corporal Ping to cool off. Just don't let this get in the way of your performance."