The Vampire Diaries, an American supernatural drama, was officially renewed by The CW for a full 22-episode season on February 16, 2010.

[3] The second season focuses on the return of Elena Gilbert's (Nina Dobrev) doppelgänger, Katherine Pierce, the introduction of werewolves, the sun and moon curse, and the arrival of the original vampires.

Meanwhile, Caroline Forbes (Candice Accola) is killed by Katherine while having Damon Salvatore's (Ian Somerhalder) blood in her system, turning her into a vampire.

The arrival of the original vampires, Elijah (Daniel Gillies) and Klaus Mikaelson (Joseph Morgan), also bring about complications.

Klaus is a vampire-werewolf hybrid, but his werewolf side had been forced into dormancy by witches, as nature would not stand for such an imbalance in power.

[27] On July 9, 2010, Entertainment Weekly announced Taylor Kinney would join the cast in a recurring role as Tyler's uncle Mason, a werewolf who comes to town after his brother dies.

[29] Michaela McManus joined the cast in a guest role as a werewolf who comes to town looking for answers about Mason's death.

On February 18, 2011, it was announced that British actor Joseph Morgan had signed on to play original vampire Klaus.

[33] The second season focuses mainly on the arrival of Elena's doppelgänger Katherine Pierce and on her reasons for returning to Mystic Falls.

Katherine's main reason for returning to Mystic Falls is to find the moonstone, with the help of Mason, who is killed by Damon.

Katherine was also a Petrova doppelgänger, who used Trevor to help her escape from the Originals and Rose to turn her into a vampire to save herself.

His brother Elijah has made a deal with Elena to protect her loved ones, because he wants to use her as bait to lure Klaus and kill him.

Jules breaks into the Salvatore mansion in wolf form and attacks Damon, but Rose pushes him out of the way, getting bitten on the shoulder instead (werewolf bites are lethal to vampires).

As Rose succumbs to the effects of the bite, Damon stakes her in a glorious dream they share, giving her a peaceful death.

Uncle John returns to Mystic Falls and comes as an unpleasant surprise to Elena, Damon, Jenna, and Alaric.

Luka becomes friends with Bonnie and tells her that Klaus will be weakened by the sacrificial ritual, meaning that Elena has to die so that Elijah can kill him and free his sister.

Stefan warns Damon and Alaric stabs Elijah, but he pulls the dagger out and tells Elena their deal is off.

When Isobel returns to town, Katherine double-crosses the Salvatores by kidnapping Elena and stealing the moonstone for Klaus in exchange for her freedom.

The site's critics consensus reads, "The sophomore season of Vampire Diaries is top shelf guilty pleasure, balancing wild twists and cliffhangers without going off the rails.

"[34] Ken Tucker of Entertainment Weekly wrote, "The throbbing red heart of The Vampire Diaries remains the tension between Damon and Paul Wesley's Stefan, and their mutual attraction to whomever Dobrev is embodying at the time.

"[35] Matt Roush of TV Guide commented, "The Vampire Diaries is the sort of show where 'never say die' is written into the mythology – a good thing for several of the opening hour's apparent victims.

I don't know how much longer The Vampire Diaries can keep churning stories at this feverish rate, but if this is your sort of guilty pleasure, you'd be crazy not to bite.