Danny Williams will say his last goodbyes to Grace on Hawaii Five-0.

Kono Goes Missing On 'Hawaii Five-0', Parents Revealed Via Flashbacks

We all new the murder of Marco Reyes would come back to haunt Danno (Scott Caan), and it looks like someone will be looking for revenge when episode 18 rolls around. The Five-0 detective will find himself locked in a Mexican prison later this season, but his thoughts will be focused on his daughter rather than his own ransom money.

"The phone call he is granted to secure cash to pay off a guard, he instead uses to say (gulp!) goodbye to Grace," TV Line revealed on Wednesday.

McGarrett Won't Trust Joe White On 'Hawaii Five-0'? EP Teases Terry O'Quinn's Return

The untitled 18th episode, which will feature the return of Joe White (Terry O'Quinn), is shaping up to be a story of dire consequences. As Danny struggles to survive his brutal captivity, Chin (Daniel Dae Kim) will also face repercussions for his role in the Reyes debacle.

"I don't know if you saw the episode last year, with Chin Ho when I.A. was investigating him, but [actor] Robert Knepper was investigating him," executive producer Peter Lenkov explained, according to Entertainment Weekly. "So this all culminates in episode 518. Robert Knepper is back and Terry O'Quinn is back...It's going to pay off everything we did in the first half of the season with regards to that arc. Danny and Chin really bent the law there, and they're not going to get away with it."

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, "Ua'aihue."

Tags: Hawaii Five-O television CBS