1) if your wife was already married at time of your marriage your marriage is null and void . your wife could not remarry during subsistence of earlier marriage .
2) if your in laws had suppressed facts about her mental condition at time of marriage you could also apply for annulment of marriage during first year of marriage on account of fraud . it cant be done now as 3 years have passed since your marriage
3) you cant be forced to have sex with your wife who is already married to some other person
4) in the event any false case is filed by your wife like 498A obtain Anticpiatory bail and contest it on merits