Shane Walsh has been best friends with Rick since the two of them were in high school; then they were partner's in the police department. When the zombie apocalypse broke out, Shane took care of Rick's wife, Lori, and son, Carl, by taking them to Atlanta. There, he becomes the leader among the group of survivors.
While in Atlanta, Shane and Lori start having relations. That ends quickly though once Rick showed up in Atlanta, alive. Lori believes that Shane had lied to her purposely telling her that Rick was dead, however Shane really did think that he had died.
Once Rick returns, there is much tension between him in Shane because the group also looks up to Rick as a leader. Shane's relationship with Lori is still kept hidden from Rick.