Lie to him and set him up for an ambush
From Create Your Own Story
You point upward and say
"He usually perches himself above the battlements so he can get a good view of your fort. There are no guards up there so you'll be safe."
Your friend thanks you and you both part ways. However your plan to ambush the RED spy has only begun. You spot a nearby alarm going up the stair case and pull it. The alarm sounds and you watch the turmoil unfold.
Every BLU team member catches the RED spy in the act of attempting to assassinate the BLU sniper. The BLU sniper himself arrives from the armory with his upgraded equipment. It is then that the RED Spy realizes his folly and accepts his fate.
The BLU team opens fire with every weapon at their disposal, Soldiers blast away with shotguns, the Sniper uses his SMG to make holes in the trespasser's body and a Heavy Weapons Guy unleashes hell with his minigun. It all ends in less than 5 seconds. The RED spy's carcass is in shreds. Thanks to you.
Your mission is complete. You have eliminated the threats of the RED team's secret weapon, effectively reduced the RED's defenses so the ensuing battle is easily won and you even managed to kill your long time enemy, the RED Sniper.
It is certainly a great victory, but not an honorable one. In the process of getting to your own objectives, you forged a facadical alliance and made deals you could not keep. You are a disgrace to all spies everywhere and are soon dishonorably discharged from the Spy Network. You soon thereafter rejoin the BLU team as an engineer.
You keep your job as an engineer for quite a while, sitting in the background eploying sentries, dispensers and the like. It's a boring and tedious job and the only one you are allowed to do. Then, one day, on a heated battlefield, the enemy breaks through your lines to detonate a large bomb in the BLU base. You are rounded up by some asshole Sniper to fight but to no avail. You are killed while trying to defend the area.
The End
