There's trouble in paradise. Hawaii Five-0 has a serious infestation of serial killers, and the Chess-Piece Killer has Steve McGarrett's task force chasing their tales.

Don't worry, however. The premiere villain may think he's a grand master, but Five-0 will bring in a few ringers to help take him (her?) down. Claire Forlani's Alicia Brown will join the hunt in episode 2, and the retired criminal profiler will help put a pin in Oahu's terrifying crime wave.

"That's an arc that's over four episodes, but the person behind it is not going to be caught," showrunner Peter Lenkov told Entertainment Weekly. "That's somebody who's still going to be in the wind, so I'm hoping that someone can come back closer to the second half, or closer to the end of the season, in order to wrap that storyline up."

How is this mysterious baddie? Lenkov is keeping a tight lid on that particular secret, but this new threat will be even more "cerebral" than Wo Fat, and he had an international crime empire under his belt.

"That story will play out over the first four episodes, and the threads from that plotline will extend through the rest of the season, with someone tied to the serial killer story line becoming Five-0's new Enemy No. 1," TV Guide teased.

As the Hawaii Five-0 crew digs back into the Chess-Piece Killer mystery, they will have a run in with MI6 in episode 2. Check out the summary for next Friday's "No ke ali'i wahine a me ka 'aina (For Queen and Country)" (see a preview below).

"Five-0 must work with rogue MI-6 agent Harry Langford (guest star Chris Vance) to find a terrorist planning to cause nuclear reactors across Europe to meltdown," CBS teased. "Also, McGarrett and Danny ask retired FBI profiler Alicia Brown (guest star Claire Forlani) to help them find their serial killer vigilante."

Catch Hawaii Five-0 Fridays at 9 p.m. ET on CBS.