One false move and I knew Sarah would be dead.

我知道萨拉一着不慎就会丧生。

《柯林斯英汉双解大词典》

One false move and the bomb might blow up.

一步弄错，炸弹就可能会爆炸。

《牛津词典》

One False Move, And You Know What?

走错一步 你知道会怎样吧?。

youdao

One false move and they could be delayed, which means they should have a greater chance of being seen and getting caught.

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Just one false move and they are out.

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Every false move seems to lead to another, more disastrous than the one before.

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