a/n completely ignores the whole bonnie's parents wanting her to go into medicine thing

Bonnie learned it from her father and some of his mechanic friends: some problems require bloodshed to solve. She first heard David say that when she was 6, as he stood over the bathroom sink, rinsing out a good-sized cut on his forearm. Her dad, standing in the hallways and leaning against the wall opposite the bathroom door, laughed and agreed.

"Why?" Bonnie asked from the doorway of her bedroom where she'd been playing. It was a familiar question from her. Why? What's that do? Why do you need to do that? Bonnie just wanted to know everything.

Her dad glanced down at his clothes to make sure nothing on them would ruin Bonnie's new shirt, then scooped her up, careful to keep her angled so she couldn't see the blood. She leaned her cheek on his shoulder. He smelled like motor oil and faintly of David's clove cigarettes.

"It's a sorta superstition we have, Bon," he explained. "We'll be fighting a stuck bolt, or maybe we can't get something aligned. If someone gets hurt and starts bleedin' it usually means everything will work out."

"Does it only work if you bleed?" Bonnie asked.

"Unfortunately yes," David chimed in. Content he'd gotten the worst of the dirt and grease out of gash, he braced himself and poured rubbing alcohol on it. He usually wouldn't bother with all that, but the Jeep they were fighting with had been sitting out in a field for months.

"Does it matter how much you bleed?" Bonnie wanted to know next.

"Sometimes," her dad answered. "Bigger problems usually require bigger sacrifices, but David went a little overboard."

Bonnie giggled at David's protests.

David gently patted the area around the wound dry with a bit of toilet paper, then stuck a large band-aid over it. "Blood's all gone!" he said after rinsing the sink and washing his hands. Bonnie twisted in her father's arms to look, but there wasn't much to see. Just a big ol' band-aid. "Maybe now that stupid door'll actually go together like it should," he added.

"It's gotta," Bonnie's dad said with a casual shrug. He set Bonnie down and kissed the top of her head. "We're back out in the garage if you need anything, Bon."

. . .

Bonnie grit her teeth and stepped back with a frustrated sigh. She'd been fighting this one bolt for five minutes now. The first starter bolt had come out easily enough, but of course the other one had to be a bitch. She'd had her wrench on the stupid thing from every angle she could get to it from and had only felt it budge once. It was like all the rust had settled on just that one bolt.

Palms sore from pushing and pulling at the wrench, Bonnie found a decently clean rag and used it to pad the wrench. If she couldn't get it in the next couple minutes, she was going to look for that can of rust remover she saw a few days ago. Martin's poor '73 Civic seemed to be hold together by a little bit of willpower and a whole lot of rust. She braced herself and slowly leaned on the wrench, careful to keep her fingers out of the way. Once she was sure the rag wasn't going to slip, she started to gently bounce on the wrench.

The bolt broke loose with an abrupt crack, causing Bonnie to lose her balance. She swore, cussing out Martin and his dumbfuck rust bucket of a car as the wrench plinkoed to the ground. She felt blood dripping from her palm as she righted herself and made her way to the shop sink with its nearby first-aid kit.

After rinsing away the worst of the blood, she inspected the wound as best she could. It didn't look bad enough to need stitches, so she cleaned and bandaged it quickly. "Alright, you little shit," she said, returning to the Civic. "I gave you blood. You got your sacrifice."

. . .

Michael had never noticed the half-inch-long scar on the upper part of Bonnie's right palm, closer to her fingers than her wrist. Then again, he didn't make a habit of staring at people's palms. He only saw it now because he was playing doctor. Much to KITT's mortification, Bonnie's annoyance, and Michael's amusement, she'd cut her inner forearm wrestling with KITT's turbo. KITT felt terrible about it, even though both humans assured and reassured him that blood loss just came with being a mechanic. No matter how well-maintained the car was or how careful you were, sooner or later you'd end up bleeding.

"It's gotta go easier now," Michael said, sticking a band-aid over the thankfully small cut. "The car gods got their sacrifice."

Bonnie perked up at that. "You too?" she asked.

"Yeah!" Michael said, laughing. "My old Chevy wouldn't let you do anything until she got her blood."

"What do you mean by that?" KITT demanded.

Bonnie and Michael both started to answer at the same time, so Michael gestured for Bonnie to go ahead and answer. "Well, it's sort of a superstitious belief that some mechanics have. If everything's fighting you and you accidentally cut yourself working on the car, it's gotta at least stop fighting every step of the way. Unfortunately, the sacrifice doesn't guarantee that it's all gonna be completely easy."

"Is that what this scar's from?" Michael asked, realizing he was still holding onto Bonnie's wrist. He let her take her hand back, and she looked down at her palm with a fondly bitter smirk.

"That poor Civic was more rust than car," she said. "I'm pretty sure it would have just fallen apart if you removed the rust from all the bolts." Michael laughed; KITT expressed his horror. "One of the starter bolts was stuck and I wasn't expecting it to break loose when it did. My hand slipped off the wrench and I cut myself." She shrugged. "The starter quit fighting so hard after that."

Sensing KITT was about to bring up the illogical nature of the whole thing, Michael stalled him for a moment or two with a story of his own: "Back when I was still with the police, a friend of mine asked me to help him find where his Jeep was leaking oil from. We couldn't find the leak, so we got things cleaned up as best we could and he went on as usual for a couple days. Rear main seal was leaking." Bonnie grimaced and groaned.

"The hard part wasn't even getting the seal replaced. Not that that was easy by any means, but yknow. The real hard part was getting the suspension back together. We had to take that poor Jeep apart a lot more than we thought. It fought us like it didn't want to be put back together. Trying to get holes lined up, I lost my balance and hit my arm hard against the frame. We didn't realize I was bleeding until we'd got the suspension bolted back in place. The Jeep got its blood."

"That's nothing more than confirmation bias," KITT scolded. It sounded like he'd expected both of them to be better than that.

"Maybe it is," Bonnie said soothingly at the same time Michael said hotly, "If it works, it ain't stupid!"

a/n michael's jeep story is mine from last summer. i was helping my dad replace the rear main seal on my own jeep and we had to take poor daisy apart more than we thought. i offered up a blood sacrifice fighting with the suspension and it went a lot more smoothly after that. i've got an inch-long scar on the outside of my right forearm