In answer to your question, here's the basic cliff notes version.
Rokk Krinn returns from the 31st century to warn Clark that he will die tomorrow at the hand of Doomsday, unless the events are altered. Rokk then gives Clark the Legion ring, informing him to use it to send Doomsday to the 31st century where the Legion is prepared to fight him. Clark refuses, insisting that it's his destiny to destroy the beast even if it means his own death. Disguised as the Red Blue Blur, Clark asks Lois to publish his final letter to the citizens of Metropolis. She asks to meet him at midnight. He agrees. In the meantime, Chloe maintains her vigilance over Davis, knowing that, in fact, he's Doomsday. Oliver seeks Clark assistance in killing Davis, but Clark's conflicted about taking a life. Instead, Clark calls upon the help of Impulse and Black Canary in his plan to simply bury the beast deep beneath Earth's surface. Oliver arrives at Clark's loft to learn that both Impulse and Black Canary have turned traitor against his wishes. Outside the geothermal facility where Clark intends to bury the beast, he's met up with Impulse and Black Canary. However, it's unknown to him that Black Canary and Impulse had no intention of assisting him, but were actually working with Oliver. Clark's then shot with a Kryptonite arrow and Oliver and his team race to the facility where Chloe's with Davis. Jimmy discovers Clark and inadvertantly learns his secret. At the facility,a fight ensues. Using black Kryptonite, Chloe splits Davis from the beast who then goes on a murderous rampage in Metropolis. Davis is still alive at this point, as well as the others. At the Daily Planet. Tess confronts Lois about the missing orb. Lois, of course, has no idea what she's talking about. Lois and Tess scuffle. Lois manages to knock Tess unconscious. Seconds later she notices the Legion ring and retrieves it. A purple light, then Lois is transported to the 31st century. Downtown, Clark is worried when Lois isn't at the phone booth, but must fight Doomsday. With all his strength, Clark propels himself and the beast into the air, then into the facility. A loud explosion follows. Jimmy reunites with Chloe at a lovely apartment he purchased. Davis arrives, and because of what he considers Chloe's betrayal, attempts to kill her. Jimmy intervenes, but is killed at the hands of Davis. Davis is, if I recall, killed at the hands of Chloe. At Jimmy's service, we learn that he was, in fact, Henry James Olsen. Chloe then offers his camera to his younger brother whose in attendance. It's likely this is James Barthlomew Olsen, the one from comic folklore. The League disperses. Clark's distraught with Lois's disappearance and Jimmy's death, and loses his faith in humanity and leaves after saying goodbye to Chloe. At the Luthor Mansion, a strange noise. Tess investigates. The symbol of Zod with a man, stark naked, standing atop it. That's what I could recall having not seen the episode in weeks. Gracious, that was tedious:) Out of 5 stars, it rates a 2. Disappointing, but that's just my opinion. The show's renewed for a ninth, by the way.