huggermugger

backdoor backstairs camouflaged clandestine classified cloak-and-dagger close confidential covert cryptic discreet disguised dissembled dissimulated furtive hush-hush in ambush incognito inside restricted secretive sly sneak sneaky

behind closed doors behind someone's back by stealth clandestinely confidentially covertly furtively hush-hush in camera in confidence in holes and corners in secret in strict confidence insidiously intimately o obscurely on the Q.T.

clandestineness clandestinity concealment confidence confidentiality covertness dark darkness furtiveness hiding huggermuggery hush isolation mystery privacy reticence retirement seclusion secretiveness secretness silence solitude