Sokka found it first. Among the brush and trees a small creature gasped for each shallow breath; its stomach rising and falling quickly. Leaning down further to inspect the animal, Sokka yelled for Katara as he realized something was wrong.
"Momo!" cried Aang as he blew the overhanging tree limbs out of his way.
Sokka had hoped that Katara would have shown up first but there was nothing he could do about it now. "I think he's hurt. I don't know what's wrong with him."
The lemur's eyes were clouded over. White foam dripped down from the side of its mouth creating a pool of saliva beneath its head. Aang reached out to pick it up but Sokka stopped him.
"Wait for Katara. Maybe she can do something," he said but doubting it.
"What," said Katara, peeking over Sokka's shoulder, "What can I do?"
"It's Momo," cried Aang, tears welling in his eyes. "There's something wrong with him."
Leaning down to the wounded animal, Katara quickly unscrewed her water canteen and enveloped her hands with the liquid. She placed them carefully atop the creature's stomach and head and concentrated. A blue, throbbing light glowed from her palms as she tried. Aang watched helplessly as a few hopeful moments passed by.
Releasing her hands, Katara looked down at the animal and saw no improvement. She turned towards Aang and frowned slightly.
"Try it again!" whispered Aang, his throat feeling choked, "Make him better again."
"It's not working," she said, looking back towards the lemur, "Momo's dying."
"Can't you do anything!" he cried, standing up above her. "Can't – can't you…" He slid back down against the trunk of a tree. The bark scraped bitterly through his clothing and cut his skin but he didn't feel it. "Go away. Both of you, please," he whispered.
Katara and Sokka exchanged a solemn look but left without a word. They walked back to Appa and discreetly told Toph what was happening.
Aang looked towards the dying creature. He sniffed and dried the sides of his eyes with his sleeve. Momo's breath became shallower and started to slow down. Aang thought about his small companion, about how scared he must be, when a thought entered his mind: maybe he still had a chance to save him. Maybe there was something in the Spirit World that could fix this!
Closing his eyes, Aang crossed his legs over one another and slowed his breathing. A few moments passed. He could still hear the small gasps for air from the lemur.
A strange breeze passed over and around his head and he opened his eyes quickly. He was still sitting in the forest and he could see Momo's body, but its spirit wasn't there. Getting up, he rushed towards the lifeless body. Colorless and dead. Turning away from the animal, Aang could see his own body rigidly sitting against the trunk of a tree. He stood there for a few moments, letting the knowledge wash over him that one of his friends was dead.
"It's not as bad as you think," said a voice behind him.
Spinning around, Aang watched as the spirit of Roku, the past Avatar, walk towards him. "What's not?" he asked.
"Death," said Roku, looking down at the lemur. "It's only the end of one thing and the beginning of another."
"But I can't just let my friends die!" cried Aang, emotion welling up inside his chest. "They're all I have."
Roku looked into Aang's eyes and frowned. "There's something that you must know, Aang. The life of an Avatar is a lonely one. You can't stay with these people for much longer or you will only endanger them further. The Avatar is the one that creates peace and tranquility for the world but not for him or herself. It has happened once or twice that an Avatar will try to have a family, a lover, a friend. It only ends in sorrow and pain."
"Why?" whispered Aang. The anger and sadness slowly seeped out of him as Roku continued to speak, an empty numbness filling him instead.
"Because there are cruel people in this world! And they will take any opportunity they can get to have control over such a powerful being like the Avatar. Even if it's through loved ones. You must understand, Aang. You need to let these companions go," Roku said, gazing sadly at the small boy.
"They're my family," said Aang, "I need them. I love them."
"You will do what is right," said the spirit, "Now go back to the real world. It is getting dark."
Roku watched as the young man's spirit joined back with his body. Aang got up hazily and wiped a few stray tears from his eyes. He slowly dug a grave for Momo's body and hoped it was deep enough to keep the animals away.
"What's the point?" asked an apelike creature next to Roku.
"What do you mean?" returned Roku, watching the boy carefully place the lemur into the hole.
"This whole Avatar business will all be over by the time the next Fire Nation Avatar comes along. No more Air benders, right? No more reincarnation," said the monkey, hanging from a tree branch.
"I wouldn't be so sure," said Roku, quietly. Putting his palms together, he silently bowed before the boy and his companion's grave. "Now come along, Momo."
"Alright," said the monkey. It walked up to the grieving boy and sprawled its hand upon Aang's forehead.
"Goodbye."