Kari has begun to get sick. Desperate to help her, Tai tries to find a cure. Kabuterimon discovers a gigantic city that has combined all of the Real World's most famous cities. With Izzy's help, Tai tries to find medicine for Kari in the city, but they find out that it's all actually Machinedramon's headquarters. As they try to dodge Machinedramon's forces, a secret about Tai's past is revealed.
Did You Know?
The title is a reference to the biblical story of Cain and Abel, in which Cain asks, "Am I my brother's keeper?" after killing his brother and God asks him where Abel is. See more
There are many errors with the city map in this episode. For example, when Izzy's laptop map shows him to be in one place, Machinedramon's map shows him elsewhere. Also, in the English dub, the Hagarumon track Izzy's laptop to "sector B-17", shown to be on the left side of the map, though when "sectors A and B" are destroyed, they're both shown to be on the right-hand side. See more
[blaming Kari's sickness on Tai
What could you have been thinking? You knew she was sick!
The English dub cuts out a moment when Tai is slapped by his mother (in the past), though there are still obvious signs of it taking place, such as Tai's red cheek, and his mother's raised hand. See more