Terror of the Saucer Race Series - Challenge! The Terror of The Blood-Sucking Saucer (恐怖の円盤生物シリーズ・挑戦！吸血円盤の恐怖 Kyōfu no enban seibutsu shirīzu - Chōsen! Kyūketsu enban no kyōfu) is the forty-third episode of Ultraman Leo. It is the fourth episode in the Terror of the Saucer Race Series (恐怖の円盤生物シリーズ Kyōfu no enban seibutsu shirīzu) story arc.
The saucer monster Demos has been called down to earth by Black Directive, and begins killing the inhabitants of Gen's town. What can the Ultra do in this situation?
Demos leaves the Black Star for Earth. Its Demos Q attack humans, draining their blood. Then they flash blue and light up. There are eight mysterious murders in one night, all the work of the saucer. The police discover that the Miyama house is in the centre of the circle of murders, and warn them to be careful. Gen recognizes it as a challenge.
A man attacks Leo and tells him Demos will kill his loved ones if he does not surrender. The man tells him that until Leo allows himself to be executed, Commander Black will continue ordering his saucer creatures to kill humans. Then the man comes to his senses and Gen realizes he was mind controlled. Meanwhile, the Demos Q crawl unnoticed into the homes of everyone in the town.
As the death toll increases, Gen decides to leave the town, leaving only a goodbye note for Tooru. Meanwhile, one of the Demos Q breaks into the police station. Discovered, it attacks. They open fire and bring it down, releasing the news that a UFO-like creature is responsible for the killings. Gen hears it on the radio and goes to the police. He arrives to late.
The police burn the saucer, which emits signals. The other saucers in the area arrive and attack, merging into a giant. Spraying acidic white foam, it kills more policemen and begins to destroy buildings. Gen arrives, and helps evacuate people. Tooru spots him along with Ayumi, but lose him.
Gen runs off and transforms. After saving a building he defeats the monster. Then he reunites with Ayumi and Tooru. Meanwhile, Black Directive prepares to summon yet another threat...
- Ultraman Leo Volume 11 features episodes 41-44.