Plot idea: disguise failure

Plot idea: Elaborate advanced-tech disguises fail to fool low-tech aliens because they have different sensory systems.

Riker: "Greetings, friend.  We have come from the village of Barsoom, three days' travel from here."

Villager: "Uh, greetings to you.  Uh, no offense, but what's wrong with your face?"

Riker: "My face?  What about it?"

Villager: "There's something... wrong.  I don't... Your forehead.  Your nose.  They're...  Healer Radek!  Come here, quickly!  Look at these travelers."

Radek: "Yes?  What... Your nose.  Your forehead.  To my bright-sight, they appear normal.  But to my dark-sight... you have no blood circulation there.  No perspiration.  No family markers.  What has happened?"

Riker: "Family markers?"

Radek: "All of you, in your party.  You all have this.  Is it a plague?  Stay back!"

Riker: "What do you mean, 'family markers'?"

Villager: "You don't know... what are you?"