How did Annie know Armin was lying?


When Armin approaches Annie in an alley to ask her to help Eren escape, Annie
agrees but puts on her ring (with the blade). Armin later realizes that she
knew from that moment that he was lying. How?




The answer is in chapter 31.

[![Annie noticing Armin's look on her
changed.](https://i.stack.imgur.com/wtzH5.jpg)](https://i.stack.imgur.com/wtzH5.jpg)

Annie noticed that Armin is not looking at her like before. Maybe she detected
hints of fear on Armin's eyes, which means Armin knows that Annie is the
Female Titan.




The answer is in chapter 31.

[![Annie noticing Armin's look on her
changed.](https://i.stack.imgur.com/wtzH5.jpg)](https://i.stack.imgur.com/wtzH5.jpg)

Annie noticed that Armin is not looking at her like before. Maybe she detected
hints of fear on Armin's eyes, which means Armin knows that Annie is the
Female Titan.

