Behold Eck! (S02E03)

Quite by chance, eye-specialist James Stones fashions several pairs of glasses which enable his patients to see an otherwise invisible, horrendous two dimensional monster. The creature attacks each patient, not to do harm but merely to take away his glasses. Using his own pair of special lenses, Dr. Stone discovers that all the creature wants is to find a way back to the outer world, whence he came accidentally. Failure to close this door within hours will mean the destruction of Earth. Dr. Stone, working frantically to make more lenses, is thwarted when the creature suddenly becomes visible to all and panic ensues. As the city's security forces trap the creature in a blazing room, Dr. Stone works feverishly to save him, so he can close the fateful doors that threaten the earth. The doctor succeeds, completes grinding the lenses, and enables the harmless monster to return to his two dimensional world. (iTunes)