We had made a deal before doing that. ｛That is, If anyone be discovered, just run as fast as we can to the beach.?

When two actions happened in the past one after another when describing in words the story to others, we use the past perfect tense for the first action.eg:-
(1)After we had made the deal, we did the wicked rascal.
(2)After we had made the deal, we were discovered.
(3)Before the "scoundrel" discovered, we had run away to the beach !

假設語氣的用法是滿複雜的：

敘事者的個人的「所知」及「看法」決定了「條件子句」和「結果子句」的時態：

1.現在談過去的事時，敘事者已經「知道了」條件和結局：
過去完成＋(過去式助動詞＋完成式動詞）
I Mary had practiced harder, she could have won the piano competition.
If we had stayed in that hotel, we would have died.
條件子句屬「過去未曾發生」或「過去不存在」，結果子句也屬於同一類。

If it were not for your help, I would not have succeeded.（條件子句的時間座標是現在：你到現在都一直還在幫我的忙）
If it had not been for your help, I would not have succeeded.（條件子句的時間座標是過去：當時你幫了我的忙）

2.敘事者已經「知道」條件子句所述是過去未發生或不存在的狀況，而「判定」結果子句所述「現在」或「未來」不可能實現或不存在：
過去完成＋（過去式助動詞＋原形動詞）
If we had stayed in that hotel, we would be dead now.
If I had earned some money last summer, I would go on a vacation next month.

過去完成＋（過去式助動詞＋進行式動詞）
If we had not missed the bus, we would be enjoying their concert now.

過去完成進行式＋（過去式助動詞＋進行式動詞）
If we hadn't been working hard in the past few years, things wouldn't be going so smoothly.

過去完成進行式＋（過去式助動詞＋完成式動詞）
If it had not been raining, we should have gone for a picnic.