If events or conditions conspire against something or conspire to do something, they combine in such a way that they spoil your plans.

The weather had conspired to ruin their day out. 坏天气凑在一起破坏了他们的一日游。

I'd planned a romantic evening together, but circumstances conspired against it - friends arrived unexpectedly and then Dave was called out to an emergency. 我计划两人共度一个浪漫的夜晚，可是事不凑巧——先是朋友们不期而至，接着戴夫被叫去出急诊。