1 When I arrived at the station, the train had left. first action: had left.
2 We lit the candles because the lights went off. first action: went off.
3 When I got home I discovered that somebody had broken into my flat. first action: had broken into.
4 The patient had died before the ambulance reached the hospital. first action: had died.
5 Billy had eaten all the cakes by the time the other children arrived at the party. first action: had eaten.
Ответ: See above