What if he got a guilty conscience and brought it back?

如果他问心有愧把它带回来呢？

《柯林斯英汉双解大词典》

She behaves as if she has something on her conscience.

她好像做了什么亏心事。

《新英汉大辞典》

For this is thankworthy, if a man for conscience toward God endure grief, suffering wrongfully.

倘若人为叫良心对得住神，就忍受冤屈的苦楚，这是可喜爱的。

youdao

Any belief is heresy if you haven't managed to determine that belief for yourself, if you haven't managed to determine that belief on the basis of your own conscience or through the powers of your own faculty of reason.

任何信念都是异教如果你不能自主决定那个真理,如果你不能决定这个信念,在自己的良心基础上或者是通过自己的推理能力。

耶鲁公开课 - 弥尔顿课程节选

It would be nice if the conscience of humanity had a way to express itself and make a difference.

CNN: Obama, failing on moral leadership?

So by all means, support Gary Johnson if your conscience demands it.

FORBES: Adam Serwer on Gary Johnson

If patriotic conscience can't compel Congress to work together, maybe requiring them to have some personal skin in the game will inspire them to do their job.

CNN: 'No Budget, No Pay' is no-brainer