[Steven W.]

Then perhaps he uses their own secret code word to show them that their gig is up. Even their code word is known.

That is a good guess for "Apache", too! The mind boggles! ;)

[bitt]

‘Then perhaps he uses their own secret code word to show them that their gig is up. Even their code word is known.’

Personally, I would have chosen
“Niagra FALLS!”