When our project was about to fail, the senior manager came to the rescue with her expertise and resources.

came 是动词 come 的过去式，表示"来、到来"。 to 是介词，在这里表示方向或目的。 the 是定冠词，表示特指某个事物。 rescue 是名词，意思是"救援、救助"。 came to the rescue 是一个固定短语，字面意思是"来到救援"，实际表示"出手相助、解救困境"的意思。