Lady Heather rears her ugly gorgeous head on CSI this Thursday (CBS, 9/8c), but why the unexpected encore? The vexing vixen - played by Nikita’s Melinda Clarke - is back for two reasons: to solve a strange crime, and to provide insider knowledge on that “evil” DNA gene that Langston (Laurence Fishburne) shares with MIA murderer Nate Haskell (returning guest star Bill Irwin).

Of course, we already knew that Haskell’s season-ending reappearance is right around the corner, but here’s the twist: It’s Clarke’s sixth CSI guest spot that actually kick-starts this intense, killer arc.

Former team leader Grissom’s sexually charged lady friend - who now goes by “Dr. Kessler” and is the proud recipient of a Ph.D. – shows up to help Sara and the Vegas CSIs solve an unusual case involving “human pets” (a real thing!). But as Jorja Fox puts it, “Lady Heather manages to get Langston - who she hadn’t previously met –€” under her thumb in four words or less. She hooks into him, seeing him as a new someone she can take on.”

And make no mistake, Sara knows all too well of this woman’s specific wiles.

Indeed, there are methods (and ulterior motives) to Lady Heather’s madness. “She is very educated on Langston’s history with Nate Haskell,” Clarke tells TVLine. “She knows he’s struggling with this ‘warrior’ gene and sees that something in him is absolutely boiling underneath. So, Lady Heather offers her help, unsolicited – but he’s not very receiving of it.”

Following Lady Heather’s one-episode appearance, Fox reveals that the Nate Haskell arc “is rising, and it’s going to be scary” when the elusive killer turns up… again. Says the actress, “We’re going to get really into [Langston’s struggle] in the next couple of episodes.”

Oh, and if you’re hoping that a Grissom-based catfight will breakout between Sara and Lady H, brace yourselves. “You might feel a little bit of cattiness,” Clarke teases with a laugh, though Fox promises that’s the extent of it. “I could never say that Sara likes Lady Heather,” says the CSI vet, “but there’s a level of respect there.”

[…]