There is a conversation in a room inside a house. Outside a train goes by. In the room with the conversation is a window. Outside the window there is a yard and then a wall and then a series of train tracks. Two people are having a conversation inside the room. They are across from the window. Outside the window the train goes by.
Freeze.
You draw a line, from the conversation, out the window, past the yard and the wall, to the tracks with the train that is passing, to a window of the train as it's going by. Inside the window, looking out, in the direction of the conversation, is a person in an orange sweater.