in medias res

US /ɪn ˌmiːdiəs ˈreɪs/
UK /ɪn ˌmiːdiəs ˈreɪs/
"in medias res" picture
1.

倒叙, 从故事中间开始

into the middle of a narrative or plot without a preamble

:
The novel begins in medias res, with the protagonist already in a desperate situation.
小说以倒叙开始,主人公已经身处绝境。
Many epic poems use the technique of starting in medias res.
许多史诗都采用倒叙的开篇手法。