When Kat pays a visit to the Angry Centipede, they are planning to steal some supplies from the Garrison. They ask her if she would like to go with them, as the kids in Lei Elgona really need the supplies for food. With the plan explained, Kat (codenamed Black Cat) heads to the fortress to find some specifically marked crates to throw to the Angry Centipede. As she reports back to them over the radio that she was given by them to let them know her task is complete, the alarm suddenly goes off, forcing her to flee the Bismalia in panic. She makes it safely back to the boat, and she along with the Angry Centipede return to Lei Elgona with the supplies they needed. They thank Kat for not just her help with the mission, but also for showing them something they are not used to: Trust.
The objective is to throw 40 marked crates over the walls to the Angry Centipedes. You can do so using Stasis Throw, but you mustn't shift gravity at any point. Don't worry too much about where you throw the crates, just so long as they go over the perimeter of the fort. If a soldier is nearby take him out quickly before he raises the alarm; if that happens, you'll have to start again from 0. Also make sure no other guards are around when you fight one.
After you've tossed the 40 crates overboard, make your way to the boat waiting for you at the terminal. Don't bother trying to fight the enemies in your way, just get out of there quickly to avoid unnecessary damage.