The Rockets were defeated! Peace has returned to the pokemon world! ...except not. While you both did a good job of kicking them in the face and making a dent, it didn't mean they'd be gone forever. But Atem knew it wouldn't really end with them. And besides, it's taking them a very long while to build up their forces again. So he's ready for some vacation. Or at least you both thought so.
But he's a hero-type. He can't sit still for a long time without doing something. And luckily for him he got wind of some bad things going on elsewhere in the world. So you two parted for a while.
About a day after you did you received this message-
Don't visit Viridian Forest until I say it's okay.
Well that's totally not worrisome or incriminating at all. And as usual when you have that feeling you can't stay out of things so you go anyway. You've probably got this forest all mapped out by now and won't have a lick of trouble navigating it.
Over the tops of the trees, nearer towards the exit, you hear a fight going on, however.
"You think you can get away with stealing other people's pokemon?" Definitely Atem's voice.
"Sure do. And here's how!"
A harsh wind picks up through the trees, making it hard to hear what attack is called; a pained cry follows it, however, and it is not a pokemon's. It's Atem's.
"Thanks for the new pokemon. These will sell nicely. And with your pokedex I'll have access to your P.C. too. Later loser!"
When you finally make it towards Atem you can see that the kid was using his pokemon to attack people.
1. He used Psychic. Atem is stumbling around and generally confused.
2. He used Poison Jab. Atem is lying on the ground in an increasing amount of pain.
3. He used Thunderbolt. Atem can no longer move.
4. He used Ice Beam. Atem is stuck in a block of ice.
Of course you can ignore Atem's plight (he might die though who knows) and go after the kid first.