Dh Going To India Alone This Time! Suggestions...

Why do you want to be worried about your DH??? are you worried that your inlaws will brainwash him???
he is not a small child , he is an adult....trust him....besides what can you do?? can you control the happenings at inlaws home while sitting 7 seas apart...
behave like a mature person and expect some maturity from your husband, dont try to control him like a child....

 

I can understand your situation as i've seen enough brainwashing incidents. After these incidents DH would speak exactly their words which he may not usually use.
In your case you can't stop him from going but don't look worried in front of him. Just send formal greetings to your in-laws and even after his arrival only formally enquire about in-laws. Don't give a chance to start a fight or try to know what happened there. Once you yourself begin it, he may tell you every thing and you may argue about something or the other(he may also start an argument based on your discussion) and if he doesn't tell you anything, you'd feel that he is not saying anything because of brainwashing and you may start an argument.
Best thing to do would be to be pleasant and formal/normal. This is easier said than done i know but try it.

 

I think you need to talk to your DH.
First you need to think through all the problem areas of life where you want no interference or brainwashing from your ILs. Make sure you sit and discuss what you as both as couple want in that area, your decisions should not be changed after he comes back, keep it strict....you may suggest your DH not to bring up those topics in front of your ILs, if they confront, let your DH change the topic or just make sure you are strict with your DH that those things are non compromisable....As another PP suggested, less follow up is better, once the words between your DH and you are fixed, there is no question of re discussion of that topic..less words more action will be better with your DH.. yes, I understand your insecurities, these are real problems, ILs do brainwash any opportunity they get....they will not leave this golden chance, so please be prepared for good discussions with your DH...good luck!