Your nephew won't kill anything at all...but then again nothing will intentionally attack him either. What you need to do was already alluded to above, and is something that you were taught earlier in the level...
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×Go bump the first door with Beethro so that your nephew opens the door. Then go through the door and kill the roaches from that side.
Game on,
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"
He who is certain he knows the ending of things when he is only beginning them is either extremely wise or extremely foolish; no matter which is true, he is certainly an
unhappy man, for he has put a knife in the heart of wonder."
-- Tad Williams