Shock by Robin Cook

Students and close friends Deborah Cochrane and Joanna Meissner have spotted a newspaper ad that may solve their financial problems. An exclusive and highly profitable fertility clinic on Boston's North Shore is looking for female donors, so they reckon they can do a bit of good by helping infertile couples while earning some money for themselves. Even when dark rumours surfaced of a previous donor's unexplained disappearance, the two young women remain undeterred.

Everything goes smoothly until second thoughts and curiosity prompt the pair to find out more. When stymied by a veil of secrecy, they even seek employment at the clinic in order to continue probing.

Working there under aliases, Deborah and Joanna soon discover the horrifying true nature of Dr Wingate's research - and immediately put their sanity, maybe even their lives, at risk.