🚀 go-pugleaf

I've been round the maze, killed everybody, got down in to the underground
and got into the house. The cook appears shouting help soon to be followed 
by a bunch of thugs so I pegged it upstairs explored up there and did all the 
rooms, found the parchment etc. So I'm now stuck. I can see that in the pool 
room where you fight the guy who throws you a Derringer (the small gun)
there is a suspicious bit of 'wall' behind one of the cabinets, near to where 
you find a piece of parchment on the floor, how do I move the cabinet. The 
other option for progressing in the game seems to be to try to get round all
the thugs waiting downstairs. Killing them in one go seems nearly impossible
with just a gun, so is there another way of getting rid of them, a distraction?

Thanks for any help 

Duncan