The CW has released the official description of the episode “Checkmate,” check it out.
IT’S CLARK VS ZOD IN THE SEASON FINALE – Zod (Callum Blue) unleashes his army upon the world, forcing Chloe (Allison Mack) to call in reinforcements from old friends. Zod tells Lois (Erica Durance) he is The Blur and asks her to steal the Book of Rao from Clark (Tom Welling). Torn between Clark and The Blur, Lois asks Clark to come clean with her about everything but he refuses. Chloe (Allison Mack) and Oliver (Justin Hartley) attempt to reconnect Watchtower’s satellite system in order to fight the Kandorians but to Chloe’s horror, Oliver gets caught on site and disappears. Tess attempts to stop Zod but he leaves her clinging to life. Clark and Zod battle for control of Earth.
PAM GRIER (“JACKIE BROWN,” “THE L WORD”) GUEST STARS AND PHIL MORRIS RETURNS AS MARTIAN MANHUNTER — Tess (Cassidy Freeman) creates an elaborate hoax in order to kidnap Green Arrow (Justin Hartley) and delivers him to Amanda Waller (guest star Pam Grier), who tells him that that the government is recruiting him to serve his country. However, Green Arrow escapes before they can reveal his identity. After Oliver brings Clark (Tom Welling) and Chloe (Allison Mack) up to speed, the three investigate and Clark is surprised to find John Jones (guest star Phil Morris.) investigating Oliver’s kidnapping too. Clark senses that John is keeping information from him. Oliver and Clark are shocked when Tess reveals that Amanda is after something called “Watchtower.” Waller threatens to kill Chloe unless Clark gives her the names and locations of the rest of the Justice League.
DC COMICS’ CHARACTERS HAWKMAN, STAR GIRL AND DR. FATE FROM THE JUSTICE SOCIETY OF AMERICA MEET UP WITH CLARK AND HIS TEAM IN A SPECIAL TWO-HOUR EVENT; PAM GRIER GUEST STARS — A man named Sylvester Pemberton tracks down Chloe (Allison Mack) and tells her he knows about her team of superheroes and needs their help. However, before he can explain who he is, he is attacked and killed by Icicle (guest star Wesley Macinnes). Clark (Tom Welling) and Chloe’s (Allison Mack) investigation leads Clark to the former headquarters of the Justice Society of America where he meets up with Nelson AKA Dr. Fate (guest star Brent Stait), Carter Hall AKA Hawkman (guest star Michael Shanks) and Courtney AKA Star Girl (guest star Britt Irvin). Courtney pleads with Hawkman and Dr. Fate to help her catch the killer that is targeting their group but they are reluctant to resume their duties as superheroes. Clark, John Jones (guest star Phil Morris), Green Arrow (Justin Hartley) and Chloe team up to help the JSA stop Icicle before he murders another member of the group. Meanwhile, Lois (Erica Durance) receives a package from a mysterious agency called Checkmate, run by Amanda Waller (guest star Pam Grier).
Smallville’s upcoming Justice Society-themed two-parter has added another headliner. Exec producer Kelly Souders confirms that the highly anticipated eppys (titled “Society” and slated to air in early 2010) will mark the return of Phil Morris as Martian Manhunter.
JOHN JONES IS SHOT — Clark (Tom Welling) discovers John Jones (guest star Phil Morris) was shot while working as a police officer, so Clark dons the uniform and goes undercover to find the culprit. Meanwhile, Lana (Kristin Kreuk) confronts Tess (Cassidy Freeman) and tells her Lex isn’t the man she thinks he is. Lana’s shocking news forces Tess to reevaluate her position as the head of Luthorcorp.
DAVIS STARTS TO SEE HIS DARK SIDE — Clark (Tom Welling) looks into a recent attack in a theater that may be the work of a serial killer. Suspecting it could be someone who is meteor-infected, he demands that Chloe (Allison Mack) release the names of the people she is counseling at the Isis Foundation, which causes a rift between the friends. Davis (Sam Witwer) fears that his blackouts could mean that he is the serial killer and collects evidence that may implicate him. Fearing the worst, he confesses his suspicions to Chloe.
THE JUSTICE LEAGUE RETURNS TO FIND CLARK AFTER THE COLLAPSE OF THE FORTRESS; THE NEW CEO OF LUTHORCORP COMES TO TOWN — The Justice League, led by the Green Arrow (Justin Hartley), hits the Artic in search of Clark (Tom Welling), who disappeared after the fortress collapsed. The team immediately has a confrontation with the new CEO of Luthorcorp, Tess Mercer (Cassidy Freeman). Meanwhile, Chloe (Allison Mack) is being held prisoner by a suspicious group who has discovered she has a new power, and Clark has been stripped of his powers by Jor-El.
LOIS AND CLARK’S SUPERMAN DEAN CAIN GUEST STARS – Chloe (Allison Mack) learns that a doctor, Dr. Curtis Knox (Dean Cain), has been treating meteor-infected people and removing their abilities. Desperate to get rid of her powers, Chloe makes an appointment to see him, unaware that Dr. Knox has a nefarious plan to kill his patients and harvest their organs. Meanwhile, Kara (Laura Vandervoort) cons Jimmy (Aaron Ashmore) into helping her locate her crystal and defies Clark’s (Tom Welling) order to stay on the farm after she discovers its whereabouts. Lana (Kristin Kreuk) sets up secret surveillance of Lex (Michael Rosenbaum).
CLARK FACES BIZARRO, HIS TOUGHEST ENEMY YET AND SUPERGIRL COMES TO SMALLVILLE – Clark (Tom Welling) confronts Bizarro, the last wraith from the Phantom Zone, and the ensuing fight causes the dam to break and a torrent of water rushes towards the land. Lex (Michael Rosenbaum), having just been arrested for Lana’s (Kristin Kreuk) murder, is submerged under water in a patrol car, but is saved by a mysterious young woman. Lois (Erica Durance) manages to pull Chloe (Allison Mack) to safety but her cousin is pronounced dead at the hospital. The same woman who saved Lex reappears at the Kent farm and is revealed to be Kara Kent (Laura Vandervoort) A.K.A. Supergirl, Clark’s cousin from Krypton.
MARTIAN MANHUNTER RETURNS – When Clark discovers Lionel threatened to kill him unless Lana married Lex, he goes after Lionel to silence him once and for all. Lana tells Lex she is leaving him, and Martian Manhunter makes a return appearance to help Clark stop Lex, who is trying to find the last wraith from the Phantom Zone in order to use its DNA to power his army of super soldiers. Meanwhile, Lois goes to Reeves Dam in search of information about Lex’s secret lab and is brutally stabbed by a security guard. Chloe’s secret power is revealed.
DC COMICS’ CHARACTER MARTIAN MANHUNTER COMES TO CLARK’S AID -Clark is attacked and wakes up in a mental asylum where the attending physician, Dr. Hudson, tells him he has been there for five years due to his elaborate fantasy that he has alien superpowers. In this new world, Martha is married to Lionel Luthor, Chloe is deemed insane and Lana chose Clark over Lex. Lana begs Clark to agree to Dr. Hudson’s treatments so they can be together, but when a fellow patient named John, A.K.A Martian Manhunter, tells him the good doctor is actually a phantom and he needs to kill him in order to return to reality, Clark must make the toughest decision of his life.