Dominic Monaghan to Become Someone's 'Pet' Dominic Monaghan has landed the lead role in Edna McCallion’s psychological thriller “Pet” for MGM. Monaghan will play Seth, a man who bumps into his old high school crush and quickly becomes obsessed with her. He takes her captive underneath the animal shelter where he works but soon suspects that his old flame is not who she seems to be. Dominic Monaghan to Become Someone’s ‘Pet’