The other Heelers set out to find the answers, and hopefully clear his name. Luke was not a nice person, it seems, since his great grandmother was also beaten and indecently assaulted. They aren't sure who committed that callous act on Luke's Gran at first, but when she dies, they focus on Luke's cousin, Ditch Kenny.
Later, the teenage assault victim regains consciousness, and says who beat him up. His father had gotten involved in some of his own beatings to teach the family a lesson, in particular, Luke's cousin.
The weapon used to kill Luke is analyzed, and the final answer to who killed Luke Darcy is revealed. PJ had said at one point "I felt like killing him", but did he actually do it? Did Ditch kill his cousin? Watch the episode to find out (part 1 and 2 should be viewed one after the other to get the whole story).
I have viewed both parts of this double episode many times, and have rated it highly. A good story.