Twice Bitten starts where Friday Night Bites leaves off. Merit is adjusting to finally completing the change. Her attraction to Ethan Sullivan is being put towards the back of her mind. She is concentrating on much more important things such as protecting Gabriel Keene, the shifter's pack leader. Merit has a big secret in which she is keeping from everyone. A secret society of vampires is attempting to recruit Merit. They think she could potentially be a big help. One night Merit and Ethan go on a mission to help bring the shape shifters to Chicago. It is at a bar. The leaders from all four shape shifter divisions are in attendance. At some point the bar is under the attack of gunfire. Merit, as Sentinel, is supposed to be protecting the House ruler Sullivan. In reality, Sullivan is the one to jump onto Merit and protect her from the gunfire. During the attack, Merit notices the cook is about to walk into the gunfire. She jumps out and saves the woman from any serious damage, sustaining a few injuries that heal quickly, but gaining appreciation and even respect from some of the shifters. The romance between Sullivan and Merit really picks up at this point. They stop by and pick up a world famous Chicago pizza. They take it back to Sullivan's room and open a bottle of wine. Merit has no thoughts in her mind about what is about to happen. They are enjoying the pizza when talk turns to how Sullivan put his life in danger for Merit. Talk leads to them finally sleeping together. That night everything is perfect between Merit and Sullivan. It's the next day that ruins everything. The next day, Merit and Sullivan go to yet another shifter meeting. It is there that Merit encounters a rough shifter. The shifter starts to pick a fight with Merit. He starts to physically attack her when Sullivan steps in with a little to much power. This does not help the matters between shifters and vampires. The two leave shortly after the encounter. On the way home, Sullivan tells Merit that he can no longer have a personal relationship with her. Things are too complicated between the two of them. Sullivan is the leader of the House and needs to protect all of the vampires there. But Merit makes him only want to protect her. Ethan suggests that everything must be strictly professional between them. Things get to be a little crazy between Merit and Sullivan. There is constant tension between the two. The day after the break-up, Sullivan's old mistress Lacey Sheridan shows up. This causes Merit to be pushed more towards the secret vampire society that Sullivan despises. Finally the day comes where the shifters decide to stay in Chicago. A number of different instances of violence come up. Merit helps put them to an end, but Sullivan speaks about his feelings towards Merit. Merit will have nothing to do with it. She tells him to stop. They are after all working strictly professional. The night ends, and Keene remains alive. The next day, Sullivan is hosting a party for their guest Sheridan. Sullivan have another talk inside his office. He once again tries to share how he feels with Merit. He tries to tell her how much he loves her and that the visit from Sheridan has been planned for months. The talk ends a little rough between the two. Merit leaves to go for a walk. On the walk, Keene's brother tells her to get into the limo with him because Gabriel is in danger. Once there, Merit realizes that this is a setup. She talks Gabriel from killing her childhood friend and that his brother is setting them up. Merit witness's a shifter shifting into his animal. Gabriel and his brother get into a fight. Gabriel is the winner, but at the end of the fight Merit receives a 911 page from the House. There was a breach into the house. Gabriel's brother informs them that he has sent all the mad shifter's to attack Sullivan's house. Merit makes a quick call to the secret society of vampires and then heads over to the House. Once there, she moves her way slowly towards Sullivan. At first she cannot get through their special vampire connection of minds. Once through, Sullivan thanks God that she is safe. Merit fights her way into Sullivan's office. The two fight back-to-back. They take out all the shifters and humans who pose a threat to them. Merit turns to Sullivan when he pulls her into an intense kiss. Later outside, Gabriel is making a public statement about shape shifters being real. There cover was blown by a fellow shifter healing himself. Now the world knows about shifters and vampires. At the end of the novel, Sullivan visits Merit in her room. He goes into how he was wrong about them never being able to be a couple. Last night proved that they have great chemistry fighting together. Merit turned down the offer to join the society. Her heart belongs to Sullivan's house and no other.