The blue car approaches a four-way stop behind the orange car. The orange car comes to a complete stop, then turns left. What should the driver of the blue car do?

If the blue car is approaching a four-way stop behind the orange and sees a sudden halt of the orange car then the blue car must also come to complete stop and wait for the orange car to make a move.

After clearance of the orange car, he should safely drive to the intersection and passes the intersection with utmost safety to avoid any accident