There's no key. You'll need a cherry bomb from the cherry bomb tree.
there is no key for the 3rd spy
There is no key. The first spy is rescued through the ceiling, the second one is freed by the laser Pen, and the third is blasted out of her cage by the Cherry Bomb Tree. (see related questions)
You take it to 1 of the cage to free the third spy.
There is no key for the cage. Use the Cherry Bomb from the Cherry Bomb tree at bottom right. Push it left onto the flower that throws it up and to the right. Follow it and push it left again onto the second flower, which will toss it close to the cage. Jump up and push it closer before it explodes. (You have about 40 seconds, If you fail, get another bomb and try again.)
The metal cage is too tough for the Laser Pen. You have to use the Cherry Bomb from the Cherry Bomb Tree at the lower right. (see related question)
Use the Cherry Bomb from the tree at the bottom right, which can blast open the cage. (for full solution, see related question)
Rescue the third spy by opening the cage in the greenhouse atop Balding Avenue. She will give you the Ultra Vision Glasses. (see the related question)
The "third spy" is being held in a greenhouse in a tall building on Balding Avenue. You can only get to the rooftops (above the Grease Monkey garage) when you have the Grappling Bowtie from the second rescued spy. (see the related question)
either in the building with all the Venus fly trap in the cage or in the building tied up in the in the attic
The first two are automatically untied when you reach them. To get to the first spy, go up over the ceiling. To get the second, use the laser pen from the first spy. To reach the third spy, use the grappling bowtie to reach the rooftops above Balding Avenue. You will have to blast open the cage with a cherry bomb to release the third spy. (see the three related questions)
In "Spy Island" at the end of the game to save the 3rd spy.
There is a cherry bomb tree in the bottom right corner. You pick it and push it over to the bouncy flower. Then you drop it then move it to the other flower, then move it to the spy's cage. Hurry though! It will blow up!