In Lonalulu, make your way to the church at the northern end of the main area. South of the church’s entrance, near a tree, should be a white/light blue Tockle that hands over the pastword.
Despite getting this pastword early enough, you will not be able to do anything until you have access to, and complete, Briscoletti’s Mansion. Once you do that, it might be helpful to speak with Bianca there (just in case), then head back to Chateau Felix. When you do this, you will find that a Great Sabrecat is attacking Tom. Speak to Tom and agree to help him to start the fight against the Great Sabrecat.
This isn’t really a challenging battle, as the Sabrecat mostly does physical attacks. So, that means you will want Eight use Kabuff on the party to help reduce this. Note that it can do a desperate attack, which is a critical and bypasses defense. It can also unleash a War Cry, which causes your characters to lose a turn, but this seems to have a low chance of actually connecting. The creature only has around 1100 HP total, so it shouldn’t take too long in bringing it down. After defeating the Sabrecat, it will slink off, so Tom asks you to help find way of taming it, giving you the One Crazy Cat quest.
Head on over to Briscoletti’s Mansion and speak to Bianca, telling her that you’ve seen sabrecats on your travels. She will hand over Bianca’s Ribbon, so return to Chateau Felix and interact with the Sabrecat. Tom will ask if you’ve found something to calm the creature, so say yes to have it sniff the ribbon. As thanks for saving him, he will hand over your reward, a pair of Beast Claws. You will also receive the pastword for Chateau Felix (Dusk), although you will need to wait a little bit before being able to complete that one.