Overhearing Atlas ' words , Dr. Tenenbaum intercepts Jack , and urges him to save the Little Sisters instead , giving him a plasmid that will displace the embedded sea slugs in each Sister . Overhearing Atlas ' words , Dr. Tenenbaum , the creator of the Little Sisters , intercepts Jack , and urges him to save the Little Sisters instead , giving him a plasmid that will displace the embedded sea slugs in each Sister .