大概是where引导的定语从句问题.
where 引导定语从句,前面的先行词（就是它所修饰的词）通常是表示地点的名词,如place,room,case,point,等.
引导定语从句的词有两种,关系代词（which,that等）和关系副词(where,when,why）等,它们的作用不仅连接着主从句,同时还在从句中充当一个成分.比如where就当地点状语=in which/this place等.
所以你这里讲的接介词是否指前面加介词?不能加.
This is the room where (in which) he was born.
That is the point where (from which point) he will start a new life.