Dovetailing on Bindlespin's thoughts. A progress tracker would work really well here.

Place enough pieces to track the number of rounds it takes for the Evil Plan to succeed. Assign one counter as the timer, moving it up one step each round. Assign another to the PC or PCs trying to break through. They move their counter through any number of combinations of actions. Maybe one space per two fatigue exerted, one space for creative uses of perform a stunt, one space for feats of strength just bullying past them, and X number of spaces for defeating a number of baddies or henchmen group.

I like this much better, actually. Lay it out where the players can see it, they know how long they have to stop the ritual, and see how far along the corridor they've progressed. Also, you could stick a couple events into the tracker. Maybe some part of the ritual occurs when they hit step X or the NPCs are demoralized by their progress and receive a misfortune die to their rolls when they hit step Y, or the opposite is true, they're emboldened by their progress and receive a fortune die.

keltheos said:

Really nice ideas here! That sounds like an exciting way to handle it that can set out a clear and dramatic goal for the PCs to overcome!

And it took me only the time it took to type it up to think of it. Something that a GM could easily do in the middle of a session. It's the outside of the box thinking I'm loving with WHFRP, it gives me the tools to do it instead of looking for rule-specific ways to handle every situation.

It's more of a "Here's your toolbox, now go and build!"