"The most challenging game of strategy ever created!" sayeth the box...proof that truth in advertising laws weren't quite so stringent in the early 70's.
Espionage is an advanced "roll and move" game similar to the Project KGB games from the same time period. Each player tryies to be the first to move their four spies from Mission Control to the waiting helicopters in the Abandoned Airfield. Along the way there are various pitfalls to slow the players down and "cloak and dagger" spaces which require drawing a card and doing what it says. Movement is handled by rolling the two dice and either moving one spy the sum of the two dice or two spies the amount shown on one die (i.e., a roll of "2" & "3" means you can move one spy 5 spaces or one spy 2 spaces and a different spy 3 spaces). Landing on an enemy spy sends that spy back to the nearest "safe" area, so the game is cut-throat to be sure.
Towards the end of the board, at the Guerrilla Camp, players draw a letter card for each spy that they want to pass through to the airfield. The requirement is that the player be able to spell out a word with their letter cards in order to win the game (four letter cards - one for each spy). If a player doesn't like the letter they drew, they can return it to the deck and wait until their next turn to draw another.