'Blue Bloods' Star Donnie Wahlberg
Actor Donnie Wahlberg arrives for the International Emmy Awards in New York November 19, 2012. Wahlberg stars as Danny Reagan in the CBS series "Blue Bloods." Reuters/Carlo Allegri

As “Blue Bloods” hits the small screen again on Friday, the hit police drama series promises to deliver another challenging case for the beloved Reagan family. On Season 7 Episode 15, titled “Lost Souls,” Danny (Donnie Wahlberg) and Det. Maria Baez (Marisa Ramirez) struggle to solve a crime, wherein they don’t want to catch the criminal.

It turns out that the victim was a murderer himself – he was responsible for a tragic car accident 10 years ago that killed a mother and a son. Danny and Baez feel torn when they discover the connection between the victim and the suspect. “House” alum Robert Sean Leonard has signed up as a guest star, playing the role of murder suspect Charles Beard.

He joins other “Blue Bloods” characters who will appear prominently on the Feb. 10 run including Frank (Tom Selleck), Erin (Bridget Moynahan), Jamie (Will Estes) and Eddie Janko (Vanessa Ray). The series also stars Det. Maria Baez (Marisa Ramirez), Henry (Len Cariou), Linda (Amy Carlson) and Nicky (Sami Gayle).

Spoiler alert! This update contains more "Blue Bloods" Season 7 spoilers. Read on at your own risk if you have not watched the latest episode.

According to TV Guide, Friday’s episode also features Erin, who puts Steve Schirripa (Anthony Abetemarco) in a tricky situation. She asks him to wear a wire while meeting up with an old friend, who turns out to be involved with the Russian mob.

CBS has posted a sneak peek of the Feb. 10 episode of “Blue Bloods” on its official site. In the trailer, Beard, the murder suspect, tells media that there is no justice until Lee Bukowski (Ed Heavey) is dead and buried. Danny reckons it sounds like a threat. He and Baez view a surveillance video that shows a man under an umbrella knifing another person along a dark alley. Danny comments that if it was his wife and kid who got killed, he would definitely be that man under the umbrella.

When Danny and Baez confronts Beard, he admits that he’s not sorry Bukowski is dead. While showing no remorse for the victim, he denies being responsible for the muder. “I’m not the one who killed him,” Beard says. Frank also figures in the trailer, as Danny seems to consult him about the complicated case.

“Lost Souls” is directed by Alex Chappele and written by Brian Burns. SpoilerTV named other actors and actresses who will be seen in "Blue Bloods" Season 7 episode 15, such as recurring “Blue Bloods” cast members Tony Terraciano (Jack Reagan), Andrew Terraciano (Sean Reagan), Gregory Jbara (Garrett Moore) and Robert Clohessy (Lt Gormley). The upcoming run will also feature additional guest stars including Gabriel Furman (Jesse Collins) , Kevyn Morrow (Glenn Knapp) , Kevin Corrigan (Jimmy Pearson) , Catherine Curtain (Ruth Bukowski) and Teo Rapp-Olsson (Todd Bukowski).

Find out what happens next on "Blue Bloods" Season 7, which airs in the US every Friday at 10 p.m. on CBS. In Australia, “Blue Bloods” airs on Thursdays, 10:30 pm on TEN.