Newt senses something is off and follows Grindelwald!Graves to an hide out. He doesn't actually want to go inside, but does so anyway. Inside Newt finds Grindelwald (disguised as Graves or not) playing with the poor real Graves in chains. Mocking him and forcing his body to like it all while having his way with him.

Newt watches in horror and tries to sneak out to get help but Grindelwald sees him and decides that Newt should join the fun.

Bonus:

+ Grindelwald really likes kissing/play biting Graves
++ Graves tries his best to protect Newt
+++ Newt tries to get Grindelwalds attention away from Graves but makes it worse