I was disappointed with the third case, but I enjoyed Aimee's and Otto Chan's side story.

Aimee and Otto are siblings.   Otto is autistic and does not socialize with many people.  They were always together when they were young but after their parents died, Aimee went to live overseas with their relatives while Otto refused to leave HK.  The relationship between the two of them changed since then.  When Aimee came back to HK, Otto was always following her around and drew sketches of her (for reasons we did not know at first).  We later get to know that Edwin Siu is their 'childhood' friend.  He cares for Otto and likes to bicker with Aimee.  Edwin's character is indeed abit nosy, but because of this, Otto's and Aimee's relationship managed to get better....

At first I half expected Otto Chan to be involve with a murder (technically he was...but he wasn't the murderer) due to his violent behaviour at first, but he turned to be such a sweet brother.  More so, I thought he was being creepy when he stalked Aimee around, but instead he was just worry about her safety.  Unlike 'normal' people though, he did not know how to express his worries and that's why he followed her.  On the other hand, Aimee showed little attention towards her brother.  I found it odd at first because she's a psychologist and yet, showed little empathy towards her brother's situation.

And so as the story develops, we got to see Aimee's side of the story.  Flipping through Otto's sketchbook, first there was a picture of their whole family.  In the next one, her dad was missing (or was it mom??).  The one afterwards, her mom was missing and gradually there was only Otto Chan standing alone in the last sketch.  Truth is, she cares about Otto but at the same time, was scared of what he was thinking... Furthermore, she herself have been trying to 'hide' away from her bad past and she did not want to uncover it again.  Contrary to his sister, Otto held onto these memories and refuses to let them go.

I felt that this was a very touching story, especially when Aimee comes to appreciate Otto Chan and their relationship.

Otto Chan did well in his role and he was quite funny when he read outloud the library barcodes :P  A true human computer!  It's unfortunate that we don't get to see anymore of him after this though :/  I thought he'd move in with Aimee or something but apparently not? :/