Trapped: storyboard (chapter 5)

Frisk asked MTT to bring him in the old royal scientist's laboratory for which now only  he had a key. When monsters left underground they left most of their stuff, what to say about old buildings. This lab wasn't used for years but there was a reason why young man wanted to go exactly there, and better if no one knew about it. MTT didn't really want to go underground again, like any other monster, but couldn't say no to Frisk. Even if he acted and looked weird that day, the simple explanation "i'm sick" was enough to reassure robot.
What they didn't know... someone were following them all this time.

When they got down to the lab Frisk immediately went to some old machines, activating the power and them and starting some manipulation weirdly confident about what he's doing. He answered small talks which MTT tried to start, but was too concentrated to notice how someone went into lab too.

Sans, Papyrus and Undyne, who were following weird acting Frisk until this place, stepped in the old abandoned lab. Sans tried to talk to Frisk but it wasn't very successful as he was saying "let me finish first". And this was worrying, especially with everything that happened lately. Sans started arguing with human, not listening to his friends trying to calm him down. And in some kind of rage he pulled the glasses off Frisk's face opening black heterochrome eyes. They were familiar but the idea of it was more than crazy to keep it in mind. 

Gaster stopped his games and took off medicine mask, not hiding anymore. More or less he was possessing Frisk's body to not lose time while explaining how his experiment should work. And this made Sans even angrier. How dared he???
But the argue cut short when Frisk himself asked Sans to just trust them... and skeleton stepped away...

When everything was ready, Gaster connected Frisk to the machine and started it. It was making loud weird noises and light show but in the end...

Gaster went out from the capsule of machine, went out from the void and cut from Frisk's body, who was sharing it with scientist for many years and timelines.

As much as everyone where surprised to see him... especially his sons, the short phrase "I can see" coming from exhausted Frisk cut all starting arguments.

After many years of blindness and imprisonment the two were free.