One of the Improv-players must leave the room for a short time. In the meantime, the audience decides on a reason why the player was late for work. (i.e. the tram could no longer run because the conductor became unconscious). Everybody, the boss, the audience, knows the reason why- only the one who arrived late does not. Now it is the late-comer's task to guess why he arrived late. He has to explain this to his boss who is dropping subtle hints to steer him into the right direction.
An example: The late-comer takes a fall in the dark: "You know, my wife slipped today in the morning because of the honey, that my son had dropped, so she broke her arm." Then the boss steers him in the right direction by getting him to understand that he is completely wrong: "But your wife broke her leg only last week, so now I don't believe you're being honest."
If the guessing player looks helpless, other players can intervene and help by entering the store or the office as a colleague or secretary or by calling the boss and giving small hidden hints.
Example: (see above)
The guessing player does not know yet that he came by tram. A co-worker comes in and says, that he almost got caught for dodging the fare.
Variation: Guessing the grounds for dismissal instead of the reason for being late.