[Michael.SF.]

"frail guy who doesn't look threatening to anyone."

Kind of like this guy?

[GrandJediMasterYoda]

or this creature.......

[libstripper]

Also like Julius and Ethel Rosenberg, two of the mousiest, most insignificant looking people anyone would ever see, but they betrayed our whole nuclear weapons program to the Soviets. It’s those inconspicuous, little people who disappear into the woodwork who make the best, most dangerous spies, not the James Bond types, who’re quickly neutralized or flipped.

[woodbutcher1963]

Exactly what I was thinking.