Hen and Karen Wilson are about to have the scariest Halloween of their lives.

In this exclusive TVLine sneak peek from tonight’s episode of 9-1-1 (ABC, 8/7c),

a night of trick-or-treating ends in horror when Denny is hit by a car that

slams into a house, the disgruntled driver losing control and veering off the road. It all starts out as a routine 911 call, just another accident on one of the busiest nights of the year for first responders. But when Chimney spots Mara and Jee-Yun in the crowd, everyone begins to piece together the horrifying puzzle. Hen is disillusioned by the thought of Karen as a victim as she rushes closer to the truth about the accident, only to realize something horrifying — that it’s their son whose life is at stake.

According to ABC’s official plot, which is much more light-hearted, the episode’s other major plot involves Buck’s Halloween decorations turning out to be “a little scarier than he expected.” Don’t get me wrong, Buck’s situation certainly has some scary twists, but nothing compared to your child’s life being put on the line.