Grace had warned him that morning, in one of the most uncomfortable conversations he'd had since coming to Pandora. She'd broached the delicate subject with her characteristic directness.

"Neytiri is in heat."

A spoonful of Cornflakes paused halfway to Jake Sully's mouth, and he looked up from a Na'vi language guide Norm had made for him.

"Excuse me, Doc?"

"Neytiri. In heat." She raised her eyebrows at him.

"Wait, you mean like a dog does?" Jake put the spoon down with a smile and an incredulous laugh, waiting for the joke.

"Oh, that's nice," Grace said. "I can already see the pictures forming in your head. No, not like a dog. It's – " she paused, thinking. "Look, all Na'vi women go through it. In human years, Neytiri is a little over 18. It's sort of like when a teenage girl hits puberty. But instead of menstruating every month, they experience one extended period of heightened arousal. Why are you blushing?"

Jake felt his face burning and ducked his head and cleared his throat. "Look Doc, why are you telling me this anyway?"

"Because as long as you're learning from her, you're spending the most time with her. Just keep your eyes open, huh?"

"You make it sound like I'm going into a battle or something."

"I've been teaching the Na'vi for ten years, marine, so take this for what's it worth: You'd be safer in battle."

"Okay, well, thanks for the warning, but I think I can handle it." Jake pushed his chair back. "These Cornflakes must be older than Hell's Gate. Come on, time to link in."

Grace followed him to the back of the tiny structure.

"I'm telling you this for your own good," she said, busying herself at the controls of Jake's unit. "I've been tracking Neytiri's growth since I came to this place. The Na'vi are very regular about the timing – she is definitely in heat, and probably has been for a few days. It's going to be reaching its peak soon, okay? After that it should start to back off a little."

Jake had already hopped into the machine, and he automatically dragged his legs into position.

"So, what am I supposed to expect, Doc?" Jake said, propping himself up on his elbows. "She going to throw herself at me or something?"

Grace snorted. "Aren't you confident. And no – but a spear isn't out of the question." She leaned down and pushed Jake's head back. "Look, here's a security briefing for you, and I'll even use small words: imagine a woman in a pissy mood from PMS, and combine that with a manic depressive. Oh yeah," she said, nodding at Jake's incredulous look. "She'll be up and down, and I mean way up, then way down. The other Na'vi will take it in stride. Just watch out if she decides to channel some of it towards her new pupil, huh? That Avatar was expensive."

"So what am I supposed to do?" Jake demanded, finally feeling a little nervous.

"Just try not to say anything too stupid," Grace said as she lowered the hatch. Jake heard a muffled thump as she smacked the top of it. "And for Christ's sake, don't mention this conversation to her. I'd rather keep any anger focused on you."