Got stuck in a sidequest in Arkham Origins (minor spoilers)

I'm in a really frustrating situation. I usually never take up side quests in Batman games, but due to foolishness I accidentally accepted a certain side quest, and now I'm stuck in it. Now, my main objective is 'Acquire Concussion Detonator at Batcave', and I'm at some Godforsaken place called 'Enigma's headquarters'. I just want to quit this stupid side quest and get back into the main game, but I just don't know how to do it. On the other hand, I'm not able to complete this side quest too, because of not being able to crack a certain password using the sequencer. Please help me out. How do I get rid of this side quest, and get back to the main game?

just turn and walk out, go to batcave and get the concussion nade

Thanks for your suggestion, although it wasn't that simple because the door I entered, refused to open. I had to go down some stairs to smash a computer, get some objective, and only then was I able to open that damn door.

ah. I had assumed you had already done that and were looking at the door to hack which has a jammer attached to it.