How to Acquire
In the mission Edge of the World, Corvo Attano or Emily Kaldwin must keep two members of the Grand Serkonan Guard from pushing Rapollo, a citizen of Karnaca, into the wall of light at the entrance of the Canal Plaza. The achievement will be completed once he has reached safety past the fish market on the way to the Campo Seta Dockyards.
An easy way to deal with the guards non-lethally is to attract their attention with a thrown object or by firing a crossbow bolt. Another alternative is to grab a chloroform bottle on the counter under the arcades, near the fish stands, and throw it at the guards to knock them both out. Note that, even if the protagonist distracts the guards by making sound or presenting themselves to the guardsmen, Rapollo will flee and the guards will chase him, not the protagonist.
This achievement also counts as a Special Action for the mission's score.