Prologue

It was mid greenleaf, the scorching waves from the sun beating down onto the earth below. This season had been hotter than the last, and due to the lack of rain, a drought had spread across the forest. So far, RiverClan had survived, but only just. It was obvious that something needed to be done, and fast. The only problem was, no one knew what to do. That's why Nightsky was on her way to the Moonstone, a direct order from Morningstar, the RiverClan leader, who also happened to be her sister.

The two had grown apart over the last year. At first, Nightsky assumed it was nothing more than the pressures of their duties driving them apart. After all, they were the medicine cat and leader, respectively. But as Nightsky paid more attention, she came to realize there was a tension between her and her sister, one she couldn't understand. They had always got along well, and there had never been any falling out between the two. So why was it that Morningstar always shot her uncertain looks, or that her words carried a hint of disgust?

Pausing to catch her breath, Nightsky stopped underneath the faint shade of a birch tree. Like most of the trees right now, this birch was suffering due to the lack of water. Its leaves had begun to shrivel up and were drooping. It was only a matter of time before it died. "I guess that's the way of the forest," she meowed to herself.

Standing up, Nightsky shook out her pelt and continued her journey. She was about halfway now. Pretty soon, she would be reaching the edge of the forest, and from there she would have to make her way across WindClan's moorlands. Glancing up at the sun, Nightsky cringed. It would be a long and uncomfortable trip. Thankfully, she was a medicine cat, so she should have no trouble crossing WindClan's territory.

As she stepped out from the shade of the forest, the heat of the sun became even more intense. Gulping, Nightsky picked up the pace. She wanted to get to the Moonstone as quickly as possible. It would be much cooler there.

Out of the corner of her eye, she could see plumes of smoke rising in the distance. At first, her heart sank, until she realized it was coming from the Twoleg greenleaf place. They must be fishbrained, she thought. Don't they realize there's a drought? I guess you can't expect Twolegs to have common sense.

It was evening when Nightsky reached the Mothermouth. Her entire body was aching, and her paw pads felt as if they had been burnt off. Settling outside the mouth of the cave, Nightsky began to groom herself. As she sat, she gazed out across the forest. It looked so much smaller from here and so beautiful. It was a view she had a hard time taking in every time she came here. If only she had someone to share it with...

A pang of sadness hit her, as she remembered her late mentor, Alderpelt. The old tom had passed away several moons earlier from greencough, along with a few other seasoned warriors. Nightsky had tried desperately to save them, but in the end, it hadn't been enough. As Nightsky thought back, she realized it was around this time Morningstar had begun distancing herself.

Does she really blame me for what happened? Nightsky wondered. She of all cats should know I tried my hardest!

A growl of indignation rose from her throat as she rose to her paws and marched towards the cave entrance. Angry thoughts swam through her mind as she thought about Morningstar. Alderpelt's death had to be the reason for her sister's behavior. It just had to be! Nightsky just couldn't fathom why her sister would resent her for something like this. She had tried her hardest to save him, but sometimes death was unavoidable, as harsh as that sounded.

By the time Nightsky reached the Moonstone, the moon was high in the sky. Its light shimmered through the hole in the roof, down onto the Moonstone itself, illuminating the cave in a brilliant white light. Nightsky crept forward, her eyes not fully adjusted yet. Once she was close enough, she settled down beside the cool stone and pressed her nose against it. Please share tongues with me, StarClan. I need to prove myself to my sister and save my Clan.

When she woke, she found herself underneath the shade of a willow tree. Alderpelt sat beside her, his gaze locked on the nearby river. The two medicine cats sat in silence for a moment, until Nightsky gathered the urge to speak.

"I'm so glad to see you again," she purred. This had been the first time Alderpelt had walked in her dreams. Seeing him alive and well once more, sent a jolt of happiness through her body. Her joy didn't last long though, as she realized her mentor did not share the sentiment.

"I'm troubled to see RiverClan in such distress," he sighed. "And I'm not talking about the drought."

Nightsky's ears flattened to her head. "What do you mean then?" she asked.

"Things are still unclear," Alderpelt meowed. "All I know is, troubling times are ahead."

Standing up, Alderpelt began walking towards the river. Nightsky dashed after him, not ready to leave him. She was still so confused by his words, and as she studied his face, she could see he was confused as well.

They walked along the river bank for a while, neither of them saying anything. Finally, Alderpelt stopped and pointed a paw towards the water. As Nightsky studied it, she could see images flashing through the water. They moved so fast, Nightsky could barely keep up. There was a reoccurring theme among them though: an unfamiliar silver tabby, Morningstar, and Nightsky herself. And although she couldn't quite understand what was going on, a sense of dread filled her stomach as she watched. Something terrible was happening, she just didn't understand what.

"There's a monster within RiverClan, one that will destroy everything if it isn't stopped," Alderpelt growled.

"Who is it?" Nightsky asked, her voice trembling. She turned to look back at the river, but the images had faded away by now. The rest of her dream began to fade as well. Nightsky let out yowls of protest, but before long she found herself awake once more in the Moonstone cavern.

Heart racing, Nightsky bolted down the tunnel that lead towards Mothermouth. The feeling of dread in her stomach had grown much stronger now. If only she understood what Alderpelt had been trying to tell her.

The only thing she could think of was that one of the cats in the images was the monster. But how could that be? Nightsky knew she wasn't a monster. She would never do anything to destroy RiverClan! And as angry as she was with Morningstar, she knew her sister wasn't evil either. As for the silver cat, Nightsky wasn't sure they were the monster either. Splashflower was the only cat in RiverClan who matched the cat in the dream, and Nightsky knew for a fact she would never do anything bad. She was one of the most gentle cats in all of RiverClan, and besides that, she was heavily pregnant at the moment.

Perhaps the three of us will be the ones to stop the monster? Nightsky thought optimistically. Yes, that seemed to be the most likely scenario. Nightsky was sure of it.

It was almost dawn by the time Nightsky reached camp. She would have gotten home sooner, but she had stopped to hunt and take a break. Besides the two cats keeping guard, no one else was awake yet. A sense of excitement and urgency filled her as she thought about sharing her dream with Morningstar. Perhaps this will fix things between us.

She made her way across the camp, and into Morningstar's den. The RiverClan leader was curled up in her nest, her flanks rising gently with every breath. As Nightsky approached, Morningstar lifted her head.

"Where have you been?" the RiverClan leader hissed, taking Nightsky by surprise. "You were supposed to be here hours ago!"

The fur on the back of Nightsky's neck began to bristle. "What are you so grouchy for? There's not a thorn in your nest, is there?"

"Don't be smart," Morningstar spat. "You said you would be back here shortly after moonhigh! It's almost dawn now. Did you not realize how urgent this is?"

Nightsky's claws dug into the ground. "Oh, I'm sorry. I didn't know there was a time limit to sharing tongues with StarClan! And in case you forgot, it's a long journey."

Morningstar relaxed a bit, although Nightsky could tell she was masking her anger. "Well, what did they say?" she asked, a hint of annoyance coating her words.

"I'm not sure," Nightsky admitted, shuffling her paws in the sand. "I spoke with Alderpelt, and he showed me a series of images in the river. They were moving so fast, I couldn't fully process them. He said there's a monster within RiverClan, but he didn't say who it was."

Morningstar let out another hiss. "You were supposed to ask about the drought!"

"I didn't have time!" Nightsky argued.

"You didn't even share tongues with StarClan, did you?" Morningstar accused.

Nightsky's eyes widened. "You really think I would make something like this up?"

"Well, I wouldn't put it past you, the way your head is always in the clouds!"

"I can't believe you," Nightsky growled. "We're supposed to be sisters, yet you treat me like this? What have I ever done to you to make you dislike me so much? We're supposed to be a team!"

Morningstar snorted. "You have no clue, do you? I can't say I'm surprised. You're so self-absorbed that you never take the time to notice anyone's needs. Maybe that's why Alderpelt, Dapplestream, and Applewhisker died. How you ever became the medicine cat is beyond me."

Nightsky's lips began to curl in the beginning of a snarl. "So that's what this is about? Do you really blame me for their deaths? I can't believe you. You know, I saw you in the images Alderpelt showed me. Maybe you are the monster he was warning me about. You're certainly acting like one." The words had slipped out before Nightsky could even think.

"Leave," Morningstar ordered.

"You-"

"I said get out!" Morningstar yowled.

The entrance to Morningstar's den rustled as Birchtail, the RiverClan deputy slipped inside. "Is everything alright?" he wondered, his gaze flickering between the two sisters.

"Everything is fine, thank you. I just want to be alone." Morningstar shot one final glare at Nightsky.

Nightsky held her sister's gaze, before leaving. The black medicine cat angrily crossed the clearing, her head racing. She couldn't believe Morningstar would speak to her in such a way. She was just trying to help! It wasn't her fault Alderpelt had shown her something completely unrelated to the drought. Curling up in her nest, Nightsky began to think back to her dream. As much as it hurt her, she was beginning to think her suspicions about Morningstar were right. She had changed so much since becoming leader, and after that last encounter, it only made sense that she was the monster Alderpelt had warned her about.

And whoever this silver cat was, must have been the third cat involved to stop Morningstar from destroying RiverClan.

As if StarClan was confirming her theory, a loud cry sounded from the nursery. "Splashflower's going into labor!"

Nightsky let out a purr as she jumped up, a surge of strength flowing through her body. As she made her way towards the nursery, she shot one final look at Morningstar's den. I won't let you destroy RiverClan.