This trick helps you in no way during the solo missions, but it's still pretty cool. First you have to unlock the grenade launcher and actavate it. Then, in mission one, after you get off the roof and kill the 1st guy, go through the doors. Then kill the 2nd guy. Turn the corner and blast a grenade at the pipe. Then go down the pipe. You will be in a small room. Blast away at the walla nd go through! You will be in Cassandra's office! Objective one is in the bag! P.S. This works really well to fool the other person in counter-operative mode.