Nah, I think that's Chapter 4. The one I'm on tasks you with finding the chalice, which involves bringing a special key to one of three seals... problem is, from what I've read, the correct seal is random and there's no way of telling which one it is beforehand, plus there's a nasty surprise if you do choose wrong!

I have a plan for sussing out the seals (Constance has the key, put her and Yuri in the middle to start with, abuse Yuri's Foul Play to let her go to either side, use Divine Pulse if I get it wrong) but I don't know how well that'll work in practice, what with the reinforcements that keep coming and all...