I can't open the trapdoor.

Hint 1 of 5:

The rug is in the way.

Hint 2 of 5:

It's bolted to the floor.

Hint 3 of 5:

You need to move the rug anyway.

Hint 4 of 5:

You could try cutting it away.

Hint 5 of 5:

Use the dagger from the desk drawer on the rug.