You have been separated from your Oathbound Lord and must fend for yourself until you can reunite.
This quest has no duration so you won't fail it while your Oathbound Lord is rotting in jail somewhere, but if you attack one of his faction's armies you will be branded a deserter instead. The only goal here is to reunite with your Oathbound Lord whenever possible be rejoining the army.
It is possible to end up in this quest directly from being on a mission due to your mission time expiring and your Oathbound Lord being imprisoned. Entry into this status will automatically cancel any active tasks you had so you won't fail them.