Is this grammatically correct? I mean, it is alright for me to write who "one of them" is in an entirely new sentence? Is it considered a sentence fragment and therefore grammatically incorrect?

Question

"By one look of his now unnaturally light pupils, she could tell that he had become one of them. A slave to the parasite that overrode his mind and controlled every movement of his body."

Answer 1

This is absolutely correct!