Smallville season 2 has 23 episodes.
1) Vortex
Jonathan and the reporter Nixon are trapped underground facing off over Clark. Clark catches Lex in a lie and they clash as well. Clark's ship vanishes from the basement, and Lionel is rendered blind.
-It's an exciting setup for the season to come.
2) Heat
A super hot biology teacher gets Clark’s hormones going which triggers his heat vision. Now he has to learn to control this new power before he burns down the town at every thought of Lana. The teacher turns out to be Lex’s fiancé, but there’s far more to Desiree than what meets the eye.
-The introduction to Clark's next big power opens the doors for some great uses of it down the road.
3) Duplicity
Pete finds Clark’s missing ship in a field. As Clark tries to subversively get it back he finds Pete sensitive to the deception, and their friendship is in danger as a result.
4) Red
Clark unknowingly comes into contact with red Kryptonite. He blows a ton of money, attacks his dad, and becomes a ladies’ man. He hasn't just loosened up though, he's become a true danger, and it's up to his family and Pete to stop him. At the same time Lionel becomes suspicious of what Clark can do.
-I think they overuse the personality-altering concept, but it's interesting to see Clark's friends and family having to face off against him.
5) Nocturne
Byron is kept prisoner in his own house sneaking out at night to leave Lana love poetry. She and Clark see his plight and attempt to help. They soon find that there’s a very good reason Byron is kept hidden away in the house. Meanwhile Lionel offers Martha a job which causes tension in the Kent household.
-It's a little bit cheesy, but it's a pretty decent episode.
6) Redux
School kids are somehow dying from old age in a matter of minutes. Clark investigates as usual. Meanwhile the Kent farm is in dire financial straits. Martha wants to turn to her dad, and Clark is eager to meet his grandfather. Jonathan doesn’t want the man anywhere near his family.
-The villainous part of this one is a little cheesy, but the character moments with the Kent family conflict adds strength to the episode.
7) Lineage
A strange woman approaches Clark claiming to be his mother. Of course the Kents can’t tell her why they’re so sure she has no relation to him, but she’s willing to kill to make it reality. Meanwhile Lana researches her own lineage which has been called into question.
-This one explores the mystery of Clark’s earliest days on Earth in more detail. Coming up with a logical backstory to Clark's adoption is no easy task. I don't know that this one is perfect, but it does a good job with creating emotional conflict. Clark's so-called mother is clearly disturbed, but there's a sad hopelessness to her plight.
8) Ryan
Ryan is in an institution where he’s the subject of experiments. He manages to contact Clark who breaks him out only to have the law come knocking on his door. The law may be immaterial, for Ryan’s life is in danger by a force against which Clark is helpless.
-Easily one of the most emotional episodes this season, I was glad to see Ryan come back.
9) Dichotic
Ian has his sights set on a perfect 4.0 GPA and is willing to kill for it. Both Ian and himself (he’s a human Xerox) date Chloe and Lana turning them against Clark.
-A true comic book story. It's similar in formula to the standard meteor-freak episode, but begins the trend of breaking away from the rigid rule of events.
10) Skinwalker
Caves below Smallville hold secrets that involve Clark. A Native American group is attempting to protect the caves from development by the Luthors. Clark falls hard for youngest leader of the charge, Kyla. When wolves begin attacking specific people Clark has to question Kyla and her people. How far are they willing to go?
11) Visage
Whitney returns home after being MIA. He seems fine except for amnesia, super strength, and a raging temper.
12) Insurgence
Lex discovers that Lionel has bugged his office. He decides to fight fire with fire. His infiltration team gets a nasty surprise, though, when they discover that Lionel and Martha have made a surprise trip to the office during the infiltration. The criminals now have the pair as hostages high in a secure building. Clark won’t be able to get in by the regular methods so how is he to save them? What surprises does Lionel keep in his safe? It’s not money, that's for sure.
13) Suspect
Who shot Lionel Luthor? The prime suspect is Jonathan, and the evidence is daunting. Clark turns CSI to clear his dad.
-It's more of a mystery driven story than what we usually see on the show. I enjoyed it.
14) Rush
A parasite is changing people’s personalities. When Pete gets infected he uses red Kryptonite to turn Clark into his unlikable self.
-The red K comes back again this quickly. We'll see it plenty more before the end of the series.
15) Prodigal
Lucas Luthor: gambling addict, action hero, well, not really. Lex finds his brother in the hopes of ousting Lionel. Instead Lex is left homeless begging at the door of the Kents.
16) Fever
Martha discovers a new disease the hard way, and not even Clark is immune. With both of their lives on the edge Jonathan finds himself giving up Clark’s secret to a doctor that happens to be Lex’s girlfriend.
17) Rosetta
The key is calling out to Clark. The result is Clark setting out on a path of discovery. The eccentric billionaire recluse Dr. Swann calls out to him claiming to have those answers.
-Easily one of the best episodes this season this begins some of the reveal of Clark's heritage with some strong nods to the Superman movies. Christopher Reeve guest stars.
18) Visitor
There’s a kid at school claiming to be an alien. He knows the position of Krypton and the design of the ship. Could he have come down with Clark in the meteor shower?
19) Precipice
Clark is nearly arrested for roughing up a bunch of guys that attacked Lana. The leader of the group levels a lawsuit that could ruin the Kent family. Meanwhile Helen’s old boyfriend frames Lex for assault putting him at odds with the law as well.
-Clark vs. a lawsuit? That could be interesting.
20) Witness
Clark faces off against super strong thugs, one of whom is a high school baseball hero. They are strong enough to overpower Clark, but when he proves difficult to stop they go after his parents.
21) Accelerate
Lana sees a ghost of the past: her dead childhood friend who tends to appear out of nowhere. She wants Lana to be her friend again, but she has twisted ideas of how life should work.
-Kind of a creepy episode. Those tend to be fun. There are some great effects in this episode, maybe the best of the season.
22) Calling
Clark is getting his wish for a relationship with Lana, but his life is never simple. The information from the ship has him worried that he will be a danger to the world. Lionel wants Chloe to investigate the fledgling hero.
23) Exodus
Jor El communicates with Clark in order to push him towards his destiny. Clark is convinced that the only way to live his own life is to destroy the ship.
-What makes this one even more interesting is knowing what upcoming seasons have shown us about Jor El. It raises the question of what might have happened if Clark had chosen a different path on this day.