In Foxcatcher, the wrestler Mark Schultz (Channing Tatum) is being supported by the excentric millionaire du Pont (Steve Carell).
Mark is very thankful for the purpose and trust du Pont provides him with and du Pont seems to be happy to have someone to mentor.
At some point in the movie the relationship starts to change when du Pont introduces Mark to drugs and he becomes apparently addicted. We also see him drinking a lot and not taking his training as serious as before. Mark starts to slip, but he also seems to do more things for du Pont now (cutting his hair) and changes his appearance to more of a sunny boy style.
What I did not quite understand, or maybe just missed:
Did Mark and du Pont have a sexual relationship? If yes, was it completely consensual or did du Pont force Mark into it?
I feel like this is hinted at by some scenes like the drug/hair cutting scene, but never clearly stated.
There is also a very weird scene where du Pont wakes up Mark in the middle of the night for a "wrestling" session in the gym. (Not sure if this was ambiguous.)