Since the first use of chemical warfare agents (CWA) (1915) to the recent attacks in Syria (2017) on mankind, there have been many incidents where CWA have claimed thousands of lives and left many more contaminated. In order to provide the appropriate and immediate medical counter measure to the victims, the exact classification of these chemical agents within few minutes on the field itself using a rapid and simple detection technique is extremely important to save the lives of the effected people. This has motivated all of us to explore the novel strategies/detection systems that can be field deployable with better selectivity and greater sensitivity. In view of this, we present a novel chemosensor, 3,6-bis(dimethylamino)-9(10H)-acridine thione (1), that can detect mustard gas and its simulant by both chromogenic and fluorogenic methods. For the first time, a single probe was able to demonstrate the detection with unprecedented selectivity over most probable interferences (nerve agents and alkylating agents) including solvents, acids, and bases which are routinely present in the environment. The desired level of sensitivity by naked eyes (0.04 mg/mL), UV spectroscopy (0.02 mg/mL), and fluorescence spectroscopy (0.005 mg/mL) makes this method truly field deployable. For the spot detection on the affected areas, a handy and potable chemosensor kit was also fabricated. This paper provides a simple, highly specific, and easy to use method in "actual sense" that not only detects the agents in the solution phase but also in the contaminated samples.