Complex sentence: Since the authorities refuse to believe that their baby has been taken, the parents call on the B.P.R.D., who send Hellboy to investigage, exposing Gruagach by seizing him with iron tongs which burn him and reveal his true form.
Split into simpler sentences: Since the authorities refuse to believe that their baby has been taken, the parents call on the B.P.R.D., who send Hellboy to investigage. Hellboy exposes Gruagach by seizing him with iron tongs, which burn him and reveal his true form.