Maybe Serena is tied up by a villainous team who wants to stop her from entering a Pokemon competition. But she uses her wits and the bond with her Pokemon to communicate with them secretly. Her Pokemon then find a way to free her just in time for her to participate in the event and defeat the villains in the end.
A possible plot could be that Serena gets tied up by some mischievous Pokemon as part of a prank. Then her friends and her Pokemon have to work together to free her in a humorous way. For example, her Pikachu could use its electric shock to cut through the ropes while the others distract the naughty Pokemon.