囚人たちは

the prisoners

→ 囚人
phrase Rare #43,006
the prisoners たち marks a group of people, and は marks the topic of the sentence.
JA: 囚人たちは庭で話していた。
EN: The prisoners were talking in the yard.

囚人たちは脱獄を試みた。

The prisoners attempted to escape.

囚人たちは釈放されて喜んだ。

The prisoners were happy to be released.