The unsolved mysteries of Gravity falls

The Best Friends

Of course our heroes found the medicine because this is what is happening in a story. Always the good win. But it wasn't so easy. Here is a detailed part of what happened.
Their footsteps were echoing from the metalic walls while they were walking
-I am kind of afraid,Stancy said. What if we don't get back in time? What if it will be too late? What if they will be gone? I will never forgive myself... It will haunt me like a ghost... Forever.....
-Don't think like that. We will find the medicine and get back to David and Finnic. This tunnel isn't as long as we thought, anyway. Look, a light!
They reach the end of the tunnel and they were in a laboratory.
-This place is huge!said Mary.
-Yeah, and full of bottles! One of them is what we need! Hurry
They ran to the nearest shelf but something cut their way. A man. It looked like the photo that is on the meat cans.
-Hello ladys! What job such beautiful girls like you have in an old and terrible place like this?
-But what job do you have blocking out way! We are in an emergency!said Mary.
-And who are you anyway? Some sort of monster, like Charlie was? Well,I am sorry I disappoint you but we beat Charlie! And we will beat you if it is necessarily! We have to save our friends!
-Well, I am sorry I disappoint you, too! I am not an ordinary monster like Charlie was....... And, by now, the play roles would roll a bit..
-What do you mean?
-I mean that now, your friends have to save you, not the opposite!
-Who are you...?asked Mary narrowing her eyes.
-My name is the Shape-Shifter, please to meet you, and this is your new grave!