Though the crew were at first under the impression that the lost ship had been found, the contents of the chest proved them wrong.

【翻译】虽然船员们开始以为已经找到了丢失的船，但箱子内的东西证明他们错了。

【分析】

1. be under the impression that... 觉得 ; 以为 ; 认为

2. contents：通常用复数，意为“内容；容纳的东西；内藏物”。例如：盒子里面的东西（内容），应说：the contents of the box，不说：the contents in the box。这个词组中the contents of the box，虽然of the box 作定语，但这里面有一层“主谓关系”： the box contains something。

3. 若改为the contents in the box，则成了地点关系，没了the box contains something 那种“主谓关系”，不符合contents 的逻辑。如果把contents 改为things，那就必须说：the things in the box，不能说：the things of the box。