这是固定搭配，没有in night的用法，但是有in the night的用法。
at night 和in the night 的区别：
1、at night 的意思是 during any night，通常表泛指。
2、in the night的意思是 during one particular night，通常表特指
相关介绍
at night的用法：
1、It was late at night, and all was quiet in the village.
夜深了，村子里沉静下来。
2、The couple wed late at night in front of just nine guests
深夜这对情侣在仅有的9位宾客面前举行了婚礼。
3、By day a woman could safely walk the streets, but at night the pavements became dangerous
白天的时候，妇女可以安全地在街上行走，而到了夜晚人行道上会变得很危险。
4、Thieves broke into the manor at night.
小偷晚上闯进了庄园。
