Mission 11: White House
Stop Reed before he kills President Caldwell.
The White House is a bloody mess in the most literal sense. The two guys down the corridor lament their trivial contributions to this mad cause. Deal with them as you wish, as a Weapon Stash is just beyond the door. At this point, Grim also gets in contact and mentions that Reed is working in cahoots with Samson to seize power from Caldwell. Expect the room beyond to be occupied by at least half dozen enemies, but feel free to be s messy and loud as possible, especially with the Weapon Stash situated so closely. Once the room is cleared and inventory has been replenished, breeze through the other rooms to the ballroom, where Samson has holed himself up along with four bodyguards. Use the pipes to launch a Death From Above/Execute show and then secure Samson.
After incapacitating Samson, immediately climb back onto the pipe and wait for the reinforcements to storm in. Among them are enemy Splinter Cells who use their goggles to locate Sam, but since he's already hanging from the ceiling they won't see him right away. Look for clusters of them and take them out in one go with Frag Grenades and Remote Mines. Feeding off the Execute gained from Samson, eliminate any remaining enemies, or save it if you can. The adjacent room boasts even more enemy Splinter Cells, but as with the previous room it has pipes running along the ceiling as well. Take out the enemies and move on.
Meet Grim in the Press Room to stop Reed and protect President Caldwell.
Jump down the elevator shaft and dispatch the guard in the dark here. The kitchen is infested with more of Reed's brutes, and you can easily Execute and Frag a good amount of them. Raid the Weapon Stash and dive from cover to cover to avoid the turret fire. Run into the corridor and stay hidden in the shadows by the farther door, as enemy Splinter Cells are preparing themselves to engage Sam. However, they're so ready that they probably won't notice him sneaking around them. Sneak past them to the next corridor with the turret. Take out the operator in the back with an explosive and continue onward.
The following rooms have Splinter Cells lying in wait; take cover and use Sonar goggles to see through their smokescreens. Continue following the waypoint marker until you meet up with Grim.
Get to the Oval Office and rescue the President.
Grim already has a plan in mind to reach Reed without endangering the President's life. She turns her gun to Sam, shoots him in the soldier, and proceeds to cuff him. Walk Sam to the Oval Office to confront Reed. Follow the in-game prompts by marking the five Splinter Cell targets and grabbing Reed. At the end, you hold the choice of sparing Reed's life or killing him (either choices gives an Achievement).
Perhaps another possible Splinter Cell game after this…?