Non-Refund of Security Deposit post peaceful vacation of Premises

I had taken a premises in Delhi Cantonment area (New Delhi region) on rent to operate a coaching centre. I stayed in this property for about 2 years. There is a proper agreement signed which was notarised. I vacated the premises on 28th Feb after serving a proper and due notice to the landlord. The landlord is holding 1 month's security deposit and is refusing to pay this money back inspite of repeated communication. The land lord is making one after the other demands all of which are unfair. After fulfilling most of his( and her) demands initially to avoid any unnecessary confrontation, and still not getting the money back, it has become clear that the land lord has no intention to pay back the security deposit which she is holding. I now need to file a case of illegally holding on to my legitimate money. Kindly share the procedure that I need to follow. My queries are: Do I need to file a police case first? If yes, is there a way to file a case on line? In case the police case is necessary to pursue a legal case, do I need to file a case in the police station where the property is located or I can file a case in a different area although in the same city? Even after the police case or in case a police case is not needed, what is the process to file a legal case and expect that my case is taken up in a local court as soon as possible? I request a necessary guidance to pursue this case. A detailed response will be highly appreciated. Please do add any point that I should consider as critical and bear in mind before proceeding with police and legal action. I understand that my query is very specific and not a general one. A necessary guidance will be highly appreciated.