It was a peaceful night, one of the very rare evenings when none of the benders was practicing, as they were all relaxing by the fireside. No one was really speaking. The atmosphere was very tame; the night sky was blanketed by clouds, giving the entire world a sort of sheltered feeling.

When Katara suddenly shuddered hard, gave a little gasp, and dropped her mug of tea, everyone stared at her. Toph sat straight up with a frown and turned her sightless eyes in Katara's direction.

For her part, Katara blinked, rubbed at her collarbone absently, then crouched to pick up the shards of the mug, her cheeks tinted pink.

"Katara?" said Aang worriedly. "You okay?"

"Mmm," she replied quietly. "I'm al—aaaah…!" She dropped the shards and clutched at her chest as if her heart was paining her.

Toph shouted, "Her heartrate's just doubled!"

Quicker than the eye could follow, Aang was across the fireside and kneeling beside Katara's gasping form before either Sokka or Zuko had finished rising to their feet.

"Katara?" he repeated, his voice tight with fear. "Katara, breathe slow, okay?

Toph scrambled over to them, Sokka right beside her. "Her heart rate is extremely jumpy," she whispered, anxiety tingeing her voice. "It's too fast, but then it keeps skipping a few beats at a time. And her body temperature just sank."

Aang had not needed her to add the last part—with his hand on Katara's cheek, he had felt her skin suddenly chill. Fear was a noose around his throat. "Breathe, Katara," he said in a low voice, trying hard to stay calm. "Just—keep breathing regularly, and—here, lie down…"

Between him and Sokka, they managed to get Katara flat on her back, though her hands were pressed hard to her heart and she was gasping and whimpering. The sounds tore at Aang's heart.

"What is this?" he said wretchedly, his eyes riveted to Katara's miserable form. "Why is she in pain?"

"I don't know," said Sokka in equal concern, watching his sister with a wrinkled brow. "She was fine just a few seconds ago."

"I don't know either," Toph added. "I just know her pulse suddenly jumped and she dropped the mug."

Teo wheeled over to them, his face a mask of worry. "Is there anything we can do to help?" he asked quietly.

Behind him, The Duke and Haru had also gotten to their feet, though they, like Zuko, remained on the other side of the fire, unsure of what to do.

"Blankets," said Sokka distractedly. "Toph says her body temperature lowered, so she needs to be kept warm." Teo immediately wheeled around to go fetch the blankets. Haru hurried over to help. The Duke hesitated, then asked, "Can I get her anything else? Water or something?"

Before Sokka could answer, Zuko said suddenly, "Water."

They all looked at him questioningly, Sokka suspiciously.

"It's something to do with her waterbending," Zuko said, ignoring Sokka's frown. "Waterbending powers rise and fall in strength with the phases of the moon, right? What's tonight's phase?" He looked up at the cloudy sky, unable to tell for himself.

Aang shook his head. "It's a full moon," he said. "She's never had a problem during full moons before. I've practiced bending with her a bunch of times during full moons. Neither of us has had any problems."

Zuko opened his mouth to say something else, but Katara, only half-conscious, whispered jaggedly, "C-cold…" and instantly everyone around her was crouched over her, murmuring platitudes.

Aang straightened as Teo wheeled back to them, blankets in hand. He and Sokka piled them over Katara—four in all—and tucked in the edges. She was still breathing hard.

"Toph?" said Sokka. "How's her heart sound?"

"Still irregular," muttered Toph, her eyes closed in concentration. "And—this is really, really weird…"

"What?" said Aang immediately. "What's wrong?"

"It feels like her whole body is vibrating. It's almost…humming," reported Toph slowly.

"Humming?" echoed Aang, bewildered. Sokka looked just as confused.

"And the humming is getting weaker," Toph added. "It's there, but it's really low-key."

Zuko shook his head. "It has to be her bending," he insisted. "Something's wrong with her because there's something wrong with her waterbending energy."

"Well, why am I fine?" Aang shot back.

Zuko threw his hands in the air. "You're the Avatar!" he snapped. "You're just odd!"

"Guys!" said Toph sharply. "Her heart just skipped a lot of beats. It's back to normal again, but her breathing is weaker."

Aang's eyes went bright with frustrated, self-directed rage. "What is going on?" he growled to no one in particular.

Zuko glared at him. "Will you at least think about my suggestion?" he snapped. "Instead of just dismissing it?"

Aang whirled to face him, but stopped just before he made a sarcastic comment. He breathed in slowly, then let it out. "Okay," he said softly. "What would be different about tonight than any other full moon night?"

With a sigh, Zuko shook his head. "I…I don't know," he said defeatedly. "But I'm sure there's something…"

Sokka snorted. "Thanks, oh brilliant one," he said acidly. "That really helps my sister."

Zuko glowered. "Well, I don't see you coming up with any ideas!" he hissed.

Toph cut in with an impatient, "Look, both of you, just calm down, okay?" She placed a hand on the ground. "Her heart rate's going up again. And—this is weird too—even though her pulse is rising, her body temperature is still really low."

Aang fell to his knees beside Katara and put a hand on her forehead. The skin was ice-cold. "Katara," he whispered helplessly.

Zuko hesitated, then looked up at the sky. "You're sure it's a full moon?" he asked gruffly.

"Yes," said Aang quietly, his gaze fixed on Katara's face, twisted in pain.

"Because I can't see it," Zuko went on, eyes still searching the clouds.

Sokka snorted. "Well, duh, genius," he said unkindly. "It's cloudy out."

Zuko only spared him the slightest of irritated glances. "I know that," he said sharply. "But usually, when the moon is full, the light is bright enough that you can see it through cloud cover."

Sokka scowled, unable to argue with that. He looked up at the clouds. "Well, I don't see the moon," he said sullenly. "Maybe the clouds are too heavy."

"Maybe," said Zuko vaguely. He looked down at Aang. "You're sure?"

"Yes," Aang said again, looking up. "Katara and I always keep track of the moon phases."

Zuko frowned. "This doesn't make sense," he mumbled to himself. "It has to be related to her bending, but this hasn't ever happened before. Full moon…full…" He trailed off, his eyes widening.

"The moon," he whispered.

Sokka sighed loudly. "Right, you've already said—"

"Aang," Zuko said over Sokka. "Something's wrong with the moon. That's got to be the only reason Katara's waterbending would be affecting her this way."

Aang frowned up at him. "Wrong with the moon?" he repeated. "But—" His eyes widened too. "The red eclipse," he said quietly. "The last time her bending suffered was during that red eclipse of the moon, when Zhao killed the moon spirit."

Sokka flinched hard at the reminder.

Aang ignored that and pressed Zuko, "You think it's an eclipse?"

"That's got to be the only reason," Zuko agreed. He looked up. "If there weren't so many clouds, I could—"

Aang got to his feet and strode to his glider. "I'll be right back," he said shortly, and took off into the air.

The scene around the campfire was tense and silent. No one could think of anything to say; Toph's frown lines got deeper as Katara's heartbeat fluctuated wildly.

When Aang landed a few minutes later, a grim look on his face, Zuko demanded tersely, "Well?"

"It's a total lunar eclipse," Aang said shortly. "It's not complete yet, but it won't be long before the moon is completely shadowed." He turned to Katara. "I don't understand why it's affecting her like this. And why I'm not affected."

"Zuko's right," Toph said with a shrug. "You're the Avatar. You're…weird."

"Thanks, Toph," said Aang sarcastically. "That's really helpful."

Toph sighed heavily. "You are being affected," she said severely. "Or haven't you noticed how crabby you're acting?"

"I'm crabby because Katara's hurt and I can't fix it!" Aang shouted, jamming his glider into the ground.

"Hey, Aang," said Teo softly. "Calm down."

"No!" Aang said angrily. "I need to find a way to help Katara now!"

Sokka stepped forward. "Aang," he said softly, "you can't do anything about a lunar eclipse. It's not like you can move the moon."

Aang scowled blackly, but sank to the ground beside Katara, crossing his legs and rubbing a hand gently over her cheek.

Sokka looked at him thoughtfully. "Toph is right," he said slowly. "You are being affected by the moon. Your temper is a lot shorter, and…well…you're being a lot more…"

"Touchy-feely," supplied Toph helpfully.

"Demonstrative," Sokka corrected her flatly, giving her a look. Unable to see it, Toph was unaffected.

The Duke wandered a little closer. "But why would the eclipse affect them this way?" he asked timidly. "Is this what happened during the other eclipse you talked about?"

"No," said Zuko. "That eclipse just caused the waterbenders to lose their bending for the duration of the eclipse. There was no moon because General Zhao killed the moon spirit, so the moon didn't have any power at all. That's why the waterbenders were helpless—because they get their strength from the phases of the moon."

He frowned at Katara's trembling form. "That eclipse wasn't natural…" he said slowly. "It removed the power of the moon completely. This eclipse is natural. A lunar eclipse…that's when the earth is blocking the moon from the sun, so the light of the moon is mostly blocked from the earth. Which means…"

"Katara's power is being blocked," finished Haru, coming to stand beside Zuko, his face troubled. "But why is it affecting her like this?" His eyes went to Aang's form. "And…why not Aang too?"

"It's got to be because Katara's body is trying to make up for not having enough energy," Toph said suddenly. "That would explain about her body temperature dropping and her heart going nutso. Her body is used to having the waterbending energy flowing through her. With the eclipse blocking that power, her body has to basically shut itself down in order to conserve what energy it does have. And it must be giving itself regular jolts to stay awake and running. That's why her heart rate keeps picking up and slowing down."

"But what about the red eclipse?" pressed Teo. "Why didn't that happen to all the waterbenders at that time?"

"Because it wasn't a natural eclipse," said Sokka slowly. "It must be because the moon's power wasn't just blocked, it was negated completely and reverted into normal energy. All the waterbending energy was reverted, too, so the body wasn't missing any."

"But this time," Teo continued excitedly, "this time the eclipse is totally natural, so the energy remains in its natural state: waterbending energy. And it's being blocked, so Toph's right, her body is trying to save its power."

"And because Katara's such a powerful bender," Sokka guessed, "her body needs a lot of that waterbending energy, so it's taking the loss really hard."

Zuko glanced at Aang. "And you," he said pointedly, "are probably not feeling the loss because you have three other types of bending energy in your body."

"So why does that make him crabbier?" The Duke asked curiously. Aang shot him a glare and The Duke ducked his head instinctively.

Toph snorted. "Because two of his energies are low right now," she said, clearly amused. "It's night, so his firebending energy is down. And it's an eclipse, so his waterbending energy is down too. That just leaves his airbending and earthbending energy."

Everyone stared at her. "So?" Zuko asked finally.

Toph shook her head. "So," she said triumphantly, "his earthbending energy is taking over his personality!"

Utter silence met that statement.

"What are you talking about?" Aang demanded.

Toph clucked in exasperation. "I mean, Twinkletoes, that you're acting like an overprotective caveman because your earth energies are sort of dominant right now. I mean, your air energies are, what, peace, calm, blah blah? Those boring things that monks teach you, right?"

Aang rolled his eyes at the slur, but nodded. "Right…"

She shrugged. "Earth is almost exactly the opposite of that, like fire is to water. Air is sort of pliant and placid, and earth is unyielding and straightforward and rough. So—" She waved a hand. "You're being unyielding and straightforward and rough. So that's why the touchy-feely, jerky attitude."

"I am not being a jerk," Aang snapped.

"Right," said Toph dryly. "So sorry, Cave Chief."

Aang opened his mouth to retort, but Sokka cut in hastily, "So Katara will be fine once the eclipse passes."

Aang looked slightly mollified at that, though his hand stayed on Katara's head, fingers tracing idly through her hair.

Zuko rolled his eyes and returned to his spot by the campfire. The Duke, Haru, and Teo followed suit. Sokka eyed Aang's sentry by Katara's side, then apparently decided to let it go and took a seat beside Toph.

Quiet returned to the little campsite.

After about ten minutes, during which Katara squirmed under the blankets and Toph gave regular reports on how fast Katara's heart was beating or how much her body temperature had risen, Toph stifled a laugh.

Sokka glanced at her. "What?" he whispered.

"Just thinking about Aang's reaction to the eclipse," she whispered back. "This is like the Avatar version of a menstrual cycle. Mood swings, caused by the moon…"

"Menstruation isn't caused by the moon," Sokka corrected her in an undertone, but he smiled.

Toph shrugged. "Still funny," she said quietly. "Aren't you glad total lunar eclipses don't happen but every so often?"

Aang looked up at them with a frown when he heard their muffled laughter. "What's so funny?" he asked.

"Nothing," said Toph innocently. Sokka beamed at him broadly.

Aang stared at them, then ordered, "Keep your voices down. You'll disturb her."

"Right." They shared a glance, then had to look away from one another quickly or else risk Aang's wrath by laughing out loud again.

--

Everyone knew, about an hour later, the moment the eclipse had passed completely, even though the clouds persistently hovered in the sky. They knew because Aang let out a huge sigh of relief when Katara stirred and opened her eyes.

"Heart's regular," said Toph boredly. "Temp's fine. Breathing's good. Can I go to sleep now?" Aang had forbidden her from dozing off in case something happened to Katara's heartbeat. Toph had replied that Aang was an earthbender too, so he could sense the vibrations as well as Toph could. He'd growled so irritatedly that she'd subsided without much more than a halfhearted mutter of complaint.

"Yeah," said Aang, smiling. "Thanks for your help, Toph." His voice fairly sparkled with his joy at Katara's wellbeing.

She sighed. "I guess you're back to normal," she muttered. She leaned slightly closer to Sokka and murmured, "Like I said, mood swings…" He choked on a laugh.

Aang didn't notice. He was leaning over Katara and whispering to her. "Are you okay now?"

She made a vague sound of confusion. "What happened to me?" she said groggily.

Toph shook her head. "Sugar Queen, between you and Prince PMS, it's been one heck of a night."

Katara frowned. "Prince Who?"

Sokka laughed. "Eclipse," he said to his sister. "You passed out. It's…sort of a long explanation. But to make it short, your waterbending energy got blocked during the eclipse, so you kind of went comatose for a little while to save your energy."

Her frown deepened. Her mind turned over Sokka's words and headed in one direction. "Aang…" She turned her head and looked up at him. "Are you okay? You didn't pass out too, did you?"

Aang flushed faintly under her concerned stare. "No, I'm fine, Katara," he said quickly. "You just need to rest and worry about yourself, okay?"

"Are you sure?" she pressed, lifting a hand to his cheek. "You should rest too. Weren't you affected by the eclipse?"

"Oh, he was affected all right," muttered Zuko from across the fire. Katara blinked. Aang blushed.

"I wasn't asking you," Katara said to Zuko sharply.

"Oh, wonderful," Toph mumbled. "They're both back to normal." Judging by the look on Zuko's face, he thought it was just wonderful, too.

"Question," Sokka said suddenly. "If Aang's earthbending energies are what caused him to be such a jerk before—"

"What?" said Katara incredulously. "Aang is not a jerk."

"You weren't conscious for it," Toph told her. "It was kind of great, really. He was being all short-tempered and crabby. And a jerk. It was cool."

Aang winced. "Was I really being—?"

"Yes," Toph answered him.

"—then what's Katara's excuse?" Sokka finished.

Silence echoed loudly.

Zuko stifled a laugh. Teo, Haru, and The Duke busied themselves by carefully staring at random objects that weren't Katara. Toph snorted appreciatively. Aang frowned.

Katara said, "Excuse me? Did you just call me a jerk?"

"I said, what's your excuse for acting like a jerk sometimes," Sokka corrected. "You're not an earthbender like Aang is, but you still show an excess of 'earth energy' a lot."

"She's a girl," said Toph. "She needs no excuse."

Katara glared at her. "And I suppose that's your excuse, too."

Toph shrugged. "Nope. Mine's the earth energy one."

Aang interrupted them. "Look, Katara, just get some rest, okay?" His eyes searched hers anxiously. "You really had us all worried."

She looked up at him, her irritation with Toph and Sokka forgotten. "I'll be fine, Aang," she said reassuringly. "You rest too." She lifted a hand from beneath the blankets and reached out.

He took it and linked their fingers together. "Okay."

They both smiled shyly at one another.

"Let me guess," said Sokka dryly. "His earth energies haven't completely subsided yet, and that's why he's being so…touchy-feely with my sister right in front of me."

Aang flushed hotly. Katara glowered at her brother.

"Nope. I'm feeling the urge to gag at the warm, fluffy feelings," Toph reported dutifully. "They are both very definitely back to normal."