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Soon, you'll catch up with Grovyle. Grovyle asks your partner to listen to him, however your partner still doesn't believe him causing Grovyle to get angry and go off. However, your partner calls after him. Your partner says that he'll/she'll listen to what Grovyle has to say...and then figure out what he/she thinks.
Grovyle explains that he wasn't really stealing the Time Gears, he was just collecting them to put them back in a place called Temporal Tower in order to let time flow, and that Dusknoir was really the villain, and how he was trying to destroy Grovyle. After this, your partner still doesn't think much of Grovyle and goes to head off somewhere. Apparently he's/she's heading off to ask Dusknoir if it's all really true. Grovyle gets upset and says that makes it a lot easier to destroy him. Additionally, before the conversation started, your partner said he'd/she'd think of what he/she thinks is right, not ask other Pokémon questions. Your partner sweats a bit and decides to go with Grovyle, since you trust him.
At the Entrance
You then make it to the entrance of Dusk Forest. Grovyle explains some more stuff and you three head off...however, what's this? Sableye appears to be hiding behind the tree, listening to your conversation all along. He goes off to report it to Dusknoir.
The entrance might remind you of the entrance of Foggy Forest. Remember how you seemed to know Foggy Forest? This is the future version of Foggy Forest. You might think the main type here is nothing at all, however, if playing In the Future of Darkness, you'll see the main type is Ghost.
After clearing this, you'll meet Celebi. Celebi will go and join your team. She's very powerful and can help you heal up with Heal Bell.
(Not that this is anything important, or not that Celebi says anything important, just make sure you talk to Celebi before entering Deep Dusk Forest!)
Deep Dusk Forest
An advanced Dusk Forest, with the main type being Ground. It isn't too hard, as now you have Grovyle and Celebi on your team, making you a complete powerhouse. Due to Heal Bell, it is unlikely you'll need a Heal Seed, or anything that restores you to your normal status.
After a bit of conversation with Dusknoir and his Sableye, Dusknoir will reveal that you, the player, was a human and Grovyle's partner, surprising you, Grovyle, and your partner.
Dusknoir and his Sableye take you away, leaving Celebi alone. Dusknoir then speaks to an unknown Pokémon, who appears to be angry. You and your partner get extremely fearful and try to run off, but Sableye holds you back. Grovyle reveals that this is Primal Dialga, a Pokémon that has to do with time. Due to time stopping, it is now going on a rampage. Dusknoir then talks to it a bit more, and then Celebi comes back to take you back to your present time. After all, there's no time like the present!