‘Pretty Little Liars’
DRAMA. Still looking for Halloween costume inspiration? The ladies of “PLL” might be able to help. The besties — including a still-living Alison, as this special flashback episode is set before she vanished — get glammed up as a witch, Mary Queen of Scots, Pocahontas, Britney Spears and Lady Gaga. Expect plenty of tricks and treats as fans get a better look at some of the secrets these girls have long been hiding.
8 p.m., ABC Family
‘Nature’
FILM. “Radioactive Wolves” isn’t a B horror flick pegged to Halloween. It’s a haunting film of another variety, documenting the wolf packs that roam the “dead zone” around the Chernobyl nuclear site.
Season premiere, 8 p.m., PBS
‘Harry’s Law’
DRAMA. Jason Alexander guest stars as a biology teacher suspended for allegedly failing a kid who rejects Darwinism. Perhaps they can work this out with the Festivus tradition of the Airing of Grievances.
9 p.m., NBC
