Seeing round corners

The two men were watching a DVD, at the end of which the man who was standing looked expectantly at the man seated behind the desk,

“Well,” he said, “what do you think?”

The man behind the desk seemed slightly confused by his colleague’s enthusiasm.  “Okay, I admit he’s convincing, he looks blind to me, but so what?”

“No, you’ve misunderstood, he really is blind. He’s not acting.”

“So, what, I don’t understand, you want me to recruit a blind spy? For the observation team? What are you, a secret agent for the equal opportunities department?”

“You’re missing the point. He’s one of those rare blind people who can navigate by echolocation. Watch the video again, he walks without any aids or guidance at all, he’s effectively sighted.”

“Okay, but I have sighted spies, why would I need a blind man?”

“You really don’t get it do you? He sees by hearing. That means he can see round corners, watch through walls, see without being seen. In other words the perfect spy.”

“Interesting. Run the DVD again, will you.”

The man played the DVD a second time.

“Why’s he keep making that ‘tch’ ‘tch’ noise as he walks?”

“That’s how he echolocates. He makes the ‘tch’ ‘tch’ noises and from the sound reverberating around him he can effectively see, like a bat, or a dolphin.”

“Well, if he can only ‘see’ by going ‘tch’ ‘tch’ all the time he won’t make much of a spy will he? He won’t exactly blend silently into the background.”

The standing man is clearly crestfallen. “Well, erm, we could use him to spy on deaf people.”