Is there an easy way to determine if the player is carrying a certain object, even if it is in a container? Unfortunately, the following does not do the trick:
The wallet is carried by the player. It is a container.
An ID card is in the wallet.
Before going north in Checkpoint Charlie:
if the player carries the ID card:
say "You briefly flash your ID to the soldier on duty. He nods at you and you walk on into an uncertain future and into the dark heart of the GDR.";
else:
say "The soldier on guard duty stands in your way. 'I'm sorry, sir, I need to see a valid piece of identification,' he says.";
stop the action.