" A Crime Within the Walls " is the of the anime series Sword Art Online (SAO). It kicks off a two-part murder mystery arc where Kirito and Asuna investigate a seemingly impossible death occurring inside a "Safe Zone". Plot Summary

This episode is the first half of a story that concludes in Episode 6: "Illusionary Avenger" .

Griselda’s husband, whose motives regarding a rare ring item drop become central to the mystery's resolution in the following episode. Guide to Watching

While Kirito and Asuna are taking a break in a town on the 57th Floor, they witness a player named Kains hanging from a window, pierced by a black spear, before his avatar shatters.

The lead investigators who begin to develop their working relationship during this arc.