@ Author
1. First you need to gain child custody knowledge. Hence read all the posts here on child visitation / custody.
2. Second you need urgently to hire a ld. Advocate specialising in child custody.
3. Third you need to file a missing / kidnap Report before your Police Stattion and take signed / stamped receipt from Police Station.
4. Forth you are required to send hand written money order to your wife with two short sentence of love and affection to her and prayer to return back and two short sentence of your fatherly love and affection to your son and desire of your child to be with her natural guardian.
5. Workout anfd file a visitation and child custody suit U/s 12,17,25 GWA R/w S. 151 CPC and FCA against mother of the child making you as petitioner one and your child as petitioner two U/G of your name Vs. State as repondent 1 and mother of child as respondent two and also file a criminal suit in a JFMC kidnap case against your FIL of kidnapping your wife and child and pray for witness evidences and call principal of the school, Police IO, your neighbours and your parents including you as witness.
I may suggest HCP as you have been seperate from your wife and child for almost 4 months now and she is held captive by your FIL against child and her wishes !. A plaint has to be worked around it. Only if you manage to get the best brains (ld. Advocate) read with your capacity to institute legal action locally then only immediately file a HCP against your State as first party, Father In Law as second party and his local police station as third party and pray before HC to produce your wife and child before the Court and also pray Lordship take counceling of both spouse in his chamber or direct party after production to refer their story for resolution to HC mediation center before disposing the HCP.