To rescue the second spy, avoid the electrified windows. To rescue the third spy, you will need to go up one building to the rooftops, then to the far left and back again. This requires the Grappling Bowtie from the second spy. (see the related question)
JUMP!
Go around them to the left. Go past the guarded building to the red building farther left. Climb to the TV tower, and then grapple back right to the antenna on the tall building's roof (a friendly spy suggests this).
On Balding Avenue, climb the building to the right of the Grease Monkey garage. Enter the "Rooftops". Put on your chameleon suit and grapple left, to the guarded building. Grapple left again, then up, and back right from the top of the red building (there is a friendly spy there).
The path to reach the third spy on Spy Island goes left from the Rooftops above the Grease Monkey garage. There is a guard who will attack you on the middle building, and no way to go straight up. So you go left to the reddish building and climb up. At the top, a helpful spy will suggest using the Grapple Bowtie to reach the tall antenna back to the right (atop the target building).
The two tallest buildings are on Balding Avenue, but to climb to the rooftops you will need the Grappling Bowtie from the second rescued spy.
After rescuing the second spy (Toupee Terrace), use the grappling bowtie to climb the building to the right of the Grease Monkey garage on Balding Avenue. Once you reach the Rooftops, you can go left onto the other buildings. (see the related question)
Wear the chameleon suit. You will need to go farther left to the red building, then climb to the top antenna. From there you can grapple to the right to reach the taller building.
The (good guys) Spy Headquarters is right where you land on Spy Island : the tall shiny building. Enter and go upstairs to get your mission from Director D.
Go farther left to the red building, climb the tower, then grapple back to the right to reach the antenna where the greenhouse is located.
jump on the windows when the lights are not on. if you touch a light you will be zapped and fall down. climb to the top of the building and cut the bars using your laser pen.
Rescue the third spy from the Rooftops above the Grease Monkey garage. You will need the Grapple Bowtie from the second spy. (see related questions)
It is the last building on Toupee Terrace. Its windows shock you if you try to climb them. But you can do it if you move carefully from window to window as the power goes on and off. You will need the Laser Pen from the first spy (at the docks) to free the second spy from the attic of this building. (see related questions)