Hawaii Five-0 will reignite an old mystery during "Umia Ka Hanu (Hold The Breath)."

'Hawaii Five-0 Season 6: McGarrett & Danny Take Their Carguments To The Friendly Skies In Sneak Peek

Last season, Grover's (Chi McBride) trust was shattered when an old friend was implicated in the murder of his wife. The former-Chicago cop couldn't get a confession during season 5, but soon Grover will take his investigation to the Windy City.

Unfortunately for McGarrett's (Alex O'Loughlin) team, Grover's absence will leave them a man down when a hostage situation puts two of their own at risk.

'Hawaii Five-0' Season 6: Goodbye Aunt Deb? Episode 12 Title Revealed

"While Grover travels to Chicago to finally get a confession from Clay Maxwell about killing his wife, Chin (Daniel Dae Kim) and Kono (Grace Park) are held at gunpoint by two killers who have no idea they are cops," CBS teased.

"Umia Ka Hanu (Hold The Breath)" won't air until Jan. 22. In the meantime, viewers can see Danny and McGarrett take on couple's therapy in "Kuleana" before Aunt Deb drops by and WWII era bombs go missing in "Ua ola loko i ke aloha."

Find out more when Hawaii Five-0 airs Fridays at 9 p.m. ET on CBS. Click the video below to see a preview for the series' next episode.

Tags: Hawaii Five-O television CBS