There are many special achievements in "Shadows of Doubt", and the answer is not just one of them. The achievement requirement of this achievement is to solve a murder case without using violence. The achievement requirement is not to knock down ( Attack) anyone, nor may flash bombs or other throwing props.
How to achieve the achievement "The Evil Shadow and Mysterious Cloud is Not the Answer"
Not the answer
Solve a murder without violence
This achievement requires successfully solving a murder case without knocking down (attacking) anyone or using flash grenades or other throwing props.
Breaking and entering does not count as a violent act (subject to change).
This achievement can be completed with "Pacifist", but is incompatible with "No One Can Run".