'Hawaii Five-0' season 7 episode 4 spoilers: Serial killer fast tracks plans, kidnaps Alicia and Steve

Last week's episode of CBS' police procedural series "Hawaii Five-0" may have presented a major turning point in the serial killer case investigated by FBI profiler Alicia Brown (Claire Forlani) and Five-0's commander Steve McGarrett (Alex O'Loughlin).

This week's follow-up episode may finally unmask the mysterious chess piece serial killer that's been preying on other serial killers in the Five-0 Task Force's backyard.

The clue is in the chess pieces found inside the mouth of every victim. When Alicia and Steve found a tome labeled "History of Medieval Chess" in Dr. Madison Gray's (Elisabeth Rohm) book shelf, they could not help but suspect the psychiatrist's involvement in the case.

Alicia had previously refused Five-0's appeal for help but her innate curiosity got the better of her. She went to do a little digging of her own and found the name of a police officer who had been investigating the serial killers before suddenly committing suicide. The officer, had been seeing Dr. Gray before presumably killing himself.

According to the official synopsis of episode 4 titled "HÅ« a'e ke ahi lanakila a Kamaile" ("The Fire of Kamile Rises in Triumph") from CBS, Alicia and Steve will find out just how close they have come to cracking the case when the chess piece serial killer kidnaps them.

As shown in the extended promo posted on Spoilers Guide, Alicia and Steve's lives will be put in danger when the killer forces them to jump into the ocean at gunpoint. They will end up in a confined pocket in the rocks that slowly fills up with sea water as the tide rises. The rest of the Five-0 Task Force will have a race against time to find and rescue them before it's too late.

But while speculations point to Dr. Gray being the chess piece killer, there is also one possible scenario wherein she may have inadvertently inspired one of her patients into a vindictive killing spree. It is also possible that she may intentionally be directing someone to do the deed for her.

The truth will soon be revealed when "Hawaii Five-0" season 7 episode 4 airs on Friday, Oct. 14 at 9 p.m. EDT on CBS.