So not sure about having to go find that "cell phone" in a different universe but that partner thing dose sound fun. They could be people that have been reincarnated because they died before their time but now they are not time locked to when they lived so they can go hunting down people that have found how to brake the time lock and are trying to distroy the past. Maybe they died because of these people who messed with time, but once they fix it there soul is now a duplicat so they keep being reborn into this pocket univeres where they became these time "cops".