There is a gate that Manny can walk through. There are fire beavers behind the gate.
Get rid of the beavers, first.
This is the low-spoiler guide for "Opening the gate" puzzle in Grim Fandango. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.