NGTV Guide: Thursday, May 6

May sweeps means the return of long-lost relatives, guest turns by spouses, and episodes written by famous authors. Hello, Thursday night!

The Vampire Diaries – the CW 8/7c
“Isobel” – Isobel (guest star Mia Kirshner) returns to town and stuns Alaric (Matt Davis) with her attitude and her demands that he arrange a meeting with Elena (Nina Dobrev.) When mother and daughter finally meet, Isobel refuses to answer most of Elena’s questions, but reveals that she will stop at nothing to find the mysterious invention Johnathan Gilbert has been searching for. Isobel’s dangerous actions lead Stefan (Paul Wesley), Damon (Ian Somerhalder) and Bonnie (Katerina Graham) to step in and help Elena deal with the situation.

Bones – FOX 8/7c
“The Witch in the Wardrobe” – A cabin burns down in the woods revealing two bodies – one of a modern-day witch and one from the days of the Salem Witch Trials – leading Booth and Brennan into the world of Wicca to find a killer. Meanwhile, when Hodgins’ reckless driving gets him and Angela arrested and thrown in jail, Sweets and intern Clark Edison (guest star Eugene Byrn) step into unfamiliar territory to help out the team. Written by Kathy Reichs.

Fringe– FOX 9/8c
“Northwest Passage” – Peter teams up with a local law enforcement official, Sheriff Mathis, on a serial murder investigation with ties to Newton. Meanwhile, Walter copes with the possibility of being sent back to St. Claire’s, and someone from the “other side” pays a visit.

Supernatural – the CW 9/8c
“Two Minutes to Midnight” – Crowley (guest star Mark Sheppard) tells Bobby (Jim Beaver) he will give him the location of Death (guest star Julian Richings), the fourth horseman, in exchange for his soul. Knowing Sam (Jared Padalecki) and Dean (Jensen Ackles) need that fourth ring to stop the Apocalypse, Bobby reluctantly agrees. Sam and Dean confront Pestilence (guest star Matt Frewer), but he unleashes a deadly virus upon them, so Castiel (Misha Collins) must intervene on their behalf. Dean has a meeting with Death to discuss Lucifer, and an unholy alliance is formed at a very high price for Dean.

The Mentalist – CBS 10/9c
“18-5-4” – Patrick Jane and the CBI team investigate the death of a mathematical genius by a gun-wielding clown. Lucy Davis (wife of Owain Yeoman) guest stars.