Click the link below if you want to read a synopsis from TVGuide.com about episode 5.10 ''In the Beginning''...
While on the trail of Lumen's former attackers, Dexter stumbles onto a possible ally, but when the homicide unit finds evidence linked to one of Dexter and Lumen's earlier victims, they are forced to throttle back. Meanwhile, Debra fingers two more suspects in the Barrel Girls investigation.
Source: TVguide.com