Sometimes, it could be a case of a mentally ill person. They might kidnap the girl on an impulse and gag her out of fear that she would escape or attract attention. They may not have a well - thought - out motive like ransom or revenge, but their actions are still very dangerous.
Once upon a time, there was a little girl named Lily. One day, when she was walking home from school, a van suddenly stopped beside her. A masked man jumped out, gagged her with a cloth, and quickly dragged her into the van. Lily was so scared but she couldn't scream. However, Lily was a smart girl. She managed to leave some small clues along the way in the van. Eventually, the police found these clues and rescued Lily, and caught the bad guy.
Perhaps it's part of a prank that has gone too far. Some irresponsible people might think it's funny to play such a cruel 'joke' on her without realizing the seriousness of their actions. However, this is still a very wrong and illegal behavior.
Perhaps she has uncovered a big secret in a corporate or political conspiracy. The people behind the conspiracy don't want her to expose them, so they tie and gag her on her tiptoes to keep her silent. They may be planning to move her to a more secluded place later to deal with her more permanently, but she might be rescued by an unexpected hero who stumbles upon the situation.
In a very imaginative story, there could be a magical or supernatural element. A soccer girl might have unknowingly entered a forbidden area on the soccer field that is protected by some magical creatures. These creatures don't understand human ways and see her as a threat, so they tie her up and use a sock to gag her to keep her from making noise that might attract other humans.
One reason could be that she is a hostage. In a thriller story, villains might gag her to prevent her from screaming for help and alerting others. For example, in a bank robbery, if the robbers take a girl hostage, they would gag her to keep her quiet during their escape.
In a horror - themed story, it might be related to a serial killer. The killer ties and gags the girl to subdue her before carrying out his evil plans. The muffled screams add to the sense of horror and helplessness, making the situation extremely terrifying for the victim.
One reason could be that the reader has stumbled upon a secret. For example, if the story is set in a world of spies, the reader might have accidentally overheard some top - secret information and the villains want to keep him quiet.
One possible reason could be for some sort of experiment. Gaster is often depicted as a mysterious scientist in the Undertale lore, and Sans has unique abilities. Maybe Gaster wants to study Sans' power over time and space. Another reason could be related to secrets. Sans might know something about Gaster's past or the true nature of the Underground that Gaster wants to keep hidden, so he kidnaps Sans to prevent him from revealing it.
One reason could be that Snape believes Hermione has knowledge that is dangerous if it falls into the wrong hands. So, he kidnaps her to keep her safe until he can figure out what to do with that knowledge. Another possibility is that he is being controlled by some dark magic or an outside force which compels him to take her against his will.
In some fanfiction, it could be due to a prophecy. Percy might think that by kidnapping Annabeth, he is fulfilling a part of a prophecy that would ultimately lead to a greater good. He could be trying to keep her away from a certain situation or enemy that the prophecy foretold. However, his way of handling it, which is kidnapping, is a very extreme measure.