When you use an exact phrase from the original passage but paraphrase the rest, the original phrase needs to be in quotation marks. For example, the passage below is from the following book (cited in APA format):
Wells, P. (2000). The Horror Genre: From Beelzebub to Blair Witch. Wallflower.
Original Passage:
"The horror genre has become increasingly concerned with the relative and fragile nature of existence."
Acceptable Paraphrase (with in-text citation to the exact page of the book):
Horror films often examine the "relative and fragile nature" of humanity and what it means to exist (Wells, p.9).