Still traveling through the Fire Nation in disguise, our heroes take shelter in a forest for the night; however, a kindly old woman discovers them, as she knows of the mysterious disappearances in the woods, and doesn't want anything to happen to the young group. Something seems decidedly odd about the lady (Hama), however, and the Gang begins to investigate - and Hama's dark secret is revealed. She's from the Southern Water Tribe.
She explains how she was a little girl when the war was relatively young, and she spent her early life in the Southern Water Tribe as a warrior. The Fire Nation had been fearful of the Avatar's rebirth into the Water Tribes, however, so one by one they captured the Water Benders, taking them away, leaving them in horrible Prisoner Of War camps, with virtually no water to bend or space to move. Hama broke out years ago, and has spent the rest of her life trying to forget her painful imprisonment.
Gleeful at having met water benders from the same tribe, Hama and Katara immediately bond, and Hama accepts to teach Katara, as she knows how dangerous is can be for a Waterbender in strange lands. She has a variety of skills to share - the ability to form water out of vapor, or suck it out of plants.
Something is still out in the woods, making people disappear, and the rest of the Gang investigates what must surely be spiritual phenomenon, even though there seems to be nothing to upset the spirits in such a beautiful town. However, they come across a hidden cave in the woods, where Fire Nation citizens have been imprisoned - controlled by their own bodies at the full moon, like some puppetmaster was controlling them. The gang realizes that Hama has discovered the darkest art of Bloodbending, controlling the fluids in another living thing, and has been using her abilities to wreak revenge on the nation which imprisoned her. But how are you supposed to fight someone who can control your body?
- Apologetic Attacker: Katara, Sokka and Aang when Hama uses bloodbending to control the boys.
- The Bad Guy Wins: Hama may be defeated, the villagers freed, but she's passed down Bloodbending to Katara, and that's what she really cares about.
- Being Tortured Makes You Evil: Hama started out as a girl who fought to protect her people, but then became obsessed with vengeance after being imprisoned in awful conditions.
- Calling Your Attacks: A rare Justified Trope in that neither Sokka nor Aang actually want to hit Katara.
- Continuity Nod: Quite a few!
- Hama mentions that ocean kumquats taste a lot like sea prunes when they're stewed long enough. Aang immediately cringes, remembering how he hated sea prunes so much in "Bato of the Water Tribe".
- In the flashback sequence, black snow is the harbinger of the Fire Nation's initial attack on a polar Water Tribe, and we see Hama and other benders trapping the Fire Nation ship.
- Sokka flips out when Toph suggests that the Moon Spirit might be vengeful.
- Dangerous Forbidden Technique: Bloodbending.
- Die or Fly: Downplayed - Katara has to either learn bloodbending or watch as Hama uses it to make Sokka kill Aang.
- The Doll Episode
- Downer Ending: The Bad Guy Wins.
- Evil Counterpart: Hama is one for Katara.
- Evil Old Folks
- Fallen Hero: Hama.
- He Who Fights Monsters: Hama falls prey to this, doing to innocent Fire Nation citizens what her Fire Nation jailers did to her.
- The Jailer: Hama
- Kubrick Stare: Hama pulls one off after she is revealed as the person behind the mysterious disappearances.
- Marionette Motion: Anyone under the influence of bloodbending.
- Misunderstood Loner with a Heart of Gold: Subverted with Hama.
- My Kung-Fu Is Stronger Than Yours: See quote at the top.
- Nice Job Breaking It, Hero: Katara figured out on her own that Hama was the one causing the disappearances and overpowers Hama's bloodbending with her own skills and power. But Aang and Sokka don't know this and think they have to save her from Hama - and unlike Katara, they can't resist the bloodbending. Cue Hama using them as puppets and Katara needing to use bloodbending to save them.
- Ominous Owl: As if to hammer home the whole Halloween episode theme, there's a shot of a cat-owl in a tree.
- People Puppets / The Power of Blood: Bloodbending is the art of controlling people's actions through the blood in their veins.
- Properly Paranoid: Sokka of Hama.
- Red Herring: Katara tells a story about a friend of her mother's who disappeared from their village as a girl. Then we meet an old waterbender from the Southern Water Tribe... who's from a generation or two further back.
- Visual Pun: After Team Avatar is told to talk to Old Man Ding, the first shot is of him placing a nail - Ding means nail.
- Xanatos Gambit: Katara was going to master the Bloodbending either willingly or under duress to save her friends.
- Your Approval Fills Me with Shame: Katara feels this way when Hama congratulates her on becoming a bloodbender.