I think he is the spy director from SPY island...
There is no secret entrance you have to get the invisible suit from Dr. Spyglass
First, you must pass Dr. Spyglass's test. Then, you can exit out of Dr. Spyglass's store. Go a little to the left, and then climb up the ladder. You will see a door. Enter it and you will be in the Lab!
You do Dr. spyglasses' eye test and he tells you to meet him up stairs. climb up the ladder and walk in the door. talk to Dr. spyglass and he gives you the chameleon suit.
You need to get the chamleon suit from dr. spyglass.
Grapple to his equipment downstairs, and press his equipments.
The suit is given to you by Dr. Spyglass, who runs the Spyglass Eyewear store. (He is secretly a spy scientist.) (see related question)
you need to fail the eye exam
You can buy the "phantom" costume in the Poptropica store, but it will not work on Spy Island to get past the guards. Get the Chameleon Suit from Professor Spyglass. (see related question)
first things first, get the chameleon suit from dr. spyglass, then use it to get inside building from top. you're only invisible when you don't move. get in, then go past dogs, and save agent, then the door will be unlocked.
Of the letter E, I can't remember what dr.spyglass can go me to go upstairs to teach what dr. spyglass is teaching E with another E to go me upstairs but in the outside,maybe the door is from that room but it's locked.
Go to the top of the SPY building and talk to the spy there. Decode his message, and you have your answer.
you ask the doctor for an exam the whatever he points to you click the opposite like this W you would put M.