Before
1. The Signalman in the middle of the night, hears a call.
2. He describes it as a call to him as if some knows he's there.
3. He is hesitant to react because it is his post and no one else's.
4. He decides to tell the narrator about this.

During
1. He decides that he must know what it is that is calling to him.
2. He investigates because there is no train.
3. He sees someone.
4. The figure disappears.

After
1. The narrator is shown in the tunnel where the call is heard.
2. He tells the signalman not to investigate it considering the accident that occurred.
3. The Signalman knows what it is.
4. He goes anyway but I will not spoil it.