Dealing with Rope Trick.

[Pigkappa]

I'm DMing an Expedition to Castle Ravenloft campaign (but you don't need to know this campaign to answer to this thread).


The group has entered the castle today to look for some items in the catacombs. They had some trouble with a few undeads and the wizards wasted their high level spells, so they decided to rest. At 11 AM. The usual, annoying 15-minute adventuring day. They cast an extended rope trick (will last 14 hours and they can cast another one when that's over) and hid inside.

What's different this time is that they did so inside the castle. The castle is populated by several intelligent creatures that are likely to consider this an offense. The owner of the castle is a level 10 wizard (and he can cast Scrying, and sometimes does). There's also a wizard3/cleric3/true necromancer5 not far from their location, and a few other intelligent creatures in the castle. The PCs have sprung a few traps, killed a few undeads and cast Rope Trick not far from there, so the NPCs know their approximate location.

The necromancer is likely to check around with See Invisibility, so that she'll notice the Rope Trick is active. However, how can she attack the PCs while they're inside? Waiting 14 hours would be annoying and would give them time to prepare their spells again, which is something I'd like to avoid if possibile.
By RAW, I think a Dispel Magic spell on the invisible window wouldn't work. But there must be some way to take them off.