This takes place during the events of Order 66 and it deals with how your OC (assuming its a Jedi and a Clone) deal with it.

Option 1: You are one of the Jedi at the Jedi Temple as the Clones began attacking, with Anakin being on their side. What do you do?

Option 2: You are on a mission in a distant planet, with nobody except the Clones and potentially your master (assuming you are still a Padawan in this time). When the order is given, what do you do next?

Option 3: Involve yourself in one of the existing Order 66 events.

Option 4: Make up something.