How to deal with situation.

I had rented a 3 bedroom flat for three persons along with me. Finding adjustment difficult landlord said us to vacate. we agreed to do so. one party vacated in September finding a place for him leaving behind two months security money which he paid through one of the tenant's account to the landlord. It is to notice that security money was transferred via one account held by the tenant. the second tenant vacates the room after one month and third is still to vacate in few days. Here the landlord says that he will charge full rent for days till any single one stays. And then he would settle the account for security deposit. I am fine with it since we rented property on full rent and we have to pay till it is vacated fully and he has right to deduct money from deposit money. the Problem arises when one tenant who left one month early he wants his security back since he left one month back itself while we two were there in flat. the landlord says he can not leave rent of one party since he has rented full flat not one room each to each party. it seems fair to me. Questions are: a) shall we two share the rent for third party since he was not there , room was locked and key handed over to the landlord. b) the third part who left room one month back is regularly sending me mail regarding return of deposit since he gave it in my account. He along with his so called lawyer sends me mail claiming me as a cheater and threatenign me to go court for 10 k of deposit. I cleared that wait till the settlement from landlord but still he sends me mail accusing me of cheating. also his lawaer calls me n advices now and then to return entire deposit money alone just becasue my account was used. C) He never bothers third tenant for money. I adviced him that if landlord takes full rent then we two shall bear rent and we would return ur money for one month. in this case his rent should be devided into two tenants who are staying now. but he says that i am fully responsible to pay him full rent back n if i dont do so he will file case against me. can a lawyer send me a mail without a case or call me n advise me to return money without meeting me or knowing facts. D) AT most the third party is not at all ready to bear his rent half because of his rude behaviour. in such situation i can not pay him alone since we two were in the flat.