Lie Detection

Lie detection is Maggie can tell when someone is lying.

Maggie
"She is able to tell if a person is lying."

- Entry on Maggie's gift

Maggie can automatically sense if a person is lying to her or to someone in close proximity. A person didn't have to speak for her to know if he or she was behaving in a way contrary to their beliefs. If anyone misrepresented themselves in either appearance or action, Maggie could feel it.

However this also has a side effect, as any kind of deception made her physically uncomfortable.

After Maggie's transformation, this ability became even more pronounced. A person didn't have to speak for her to know if he or she was behaving in a way contrary to their beliefs. If anyone misrepresented themselves in either appearance or action, Maggie knew.

Origin
When Maggie was human, she always knew when a person was lying with their words, compelling her to always point out the lie. This made others feel uncomfortable around her as they could never lie in her presence, prompting her parents to leave her behind when they immigrated to America.

Aidan Johnston
Aidan can sense if a person is lying to him or not. It has not been explained how different from Maggie's this gift is, but it appears to be less pronounced than hers.

How this power works remains unexplained, but it can be assumed that he can sense the discrepancy between the intentions in the speaker's mind and the spoken words.