On Earth there exists a very rare twin-tailed mermaid with a natural defense against lying. If she hears anyone lying to her nearby, her tongue reflexively shoots out and punches a hole through their brain.
One morning, the Color Ranger kids are saying goodbye as one of them will be going to America now that his dad's about to start working there. However, that same kid finds a young woman bleeding from her stomach and tries to go help her by apologizing to his friends. They reluctantly accept his apology and later return as the blue ranger heals her wounds with his power.
The team heads to the sewer to find the mermaid's handlers from before, who promise that they'll return her to her planet and what's left of her family if she earns enough money for them. Her tongue does not shoot out at them, but the kids are convinced they are lying and attack. Finally, it turns out that they were using devices to fool the mermaid's natural instincts, and tell her the truth: her family was sold off to others and possibly dead now. The mermaid shoots them with a normal gun in response.
Later, the mermaid says goodbye after acknowledging that she is probably the last of her kind in the universe, but she meets up with single-tailed mermaids as she swims away into the ocean.