It is strange that he (should) have left withoutsaying doodbye .在_英语解答

It is strange that he (should) have left withoutsaying doodbye .
在这句话中should怎么翻译啊?为什么可以省?说一下should的用法

人气：132 ℃　时间：2019-08-22 14:20:43

解答

It is strange that he (should) have left withoutsaying doodbye .
should:竟然
句意：他竟然一句话没说就离开了
多谢!