Midnight Sun is an intelligence agency based in the Nomad nation. Midnight Sun encourages competition between their own analysts, so these intelligence gathers will often be found in the thick of the action. For the opponents of the Nomad nation, these Midnight Sun analyst are highly valuable targets to capture.
Infinity is a scenario based game, so you'll always have main objectives you are trying to achieve in each game. There are also secondary objectives that you can go for to gain more points. Usually you will draw 1-2 cards for "Classified" objectives. Only you will know what these objectives are and they are only revealed to your opponent when successfully completed. Also, each player will put a HVT (High Value Target) in the middle of the table. You want to try to capture the opponents HVT while protecting your own. HVT's serve another purpose in that some of the classified objectives involve interaction with your opponents HVT.
So, if the previous paragraph didn't make sense, then here's the gist. Each game you have to place a non-combatant on the table and try to protect them from capture. This dude is mine!