you are likely to find Gun in/at/on Desk. you are likely to find Envelope in/at/on Desk. Envelope is a type of Bag. 
Argument would make you want to Walk. Walk is a synonym of Sidewalk. Sidewalk is related to Home. Home is related to Guard. 
Gun --AtLocation--> Desk <--AtLocation-- Envelope --IsA--> Bag 
Argument --CausesDesire--> Walk <--Synonym--> Sidewalk <--RelatedTo--> Home <--RelatedTo--> Guard 