who told you to find a secret door?
there isnt one.
you go in.. you talk to innkeeper
talk to woman. talk to group of 3 men.
go upstairs (the stairs are to the north. easily visible)
come back down the stairs (there is a hatch on the floor)
3 men will be talking to eachother. then attack you.
talk to innkeeper again
then talk to woman.
she gives you key
use key on locked door upstairs in bedroom
in chest is crystal