|Divide and Conquer|
|Publication date||Novermber 6, 2012|
| Preceded by|
A Mutiny in Time
| Followed by|
The Trap Door
Divide and Conquer is the second book in the Infinity Ring series. It was written by Carrie Ryan.
Hundreds of ships carrying thousands of Viking warriors are attacking medieval Paris. The Parisians are fighting back, but they can only hold out for so long. And that's bad news — especially since Dak has been captured and forced to work with the invading army while Sera and Riq defend Paris from within. No matter which side wins, the kids will lose . . . unless Dak can find an ally among some of history's fiercest warriors. Join Dak, Riq, and Sera as they attempt to defeat the SQ and fix the next Great Break in history.
Dak, Sera, and Riq warp to Paris 885, right before the Vikings begin their attack on the city. They take refuge in an abandoned house, where they activate the SQuare, although they cannot make sense out of the messages. The trio then goes to a meeting between Paris and the Vikings, who are led by Siegfried, where Riq steps in and, instead of having Paris agree to surrender, he purposefully misinterprets the message so Paris chooses to fight. Later, Sera finds the local Hystorian, Billfrith, aka Bill, while Dak explores a Viking ship and is caught by a Viking named Rollo, but hides the SQuare before getting caught. Thankfully, Dak escapes by befriending the guard-Rollo's fierce dog Vígi.
Meanwhile, Sera, Riq, and Bill are trying to find safety while Paris is being attacked, but Riq is led out to battle while Sera and Bill hide in an old turret. Dak, now in the middle of the battle, becomes the standard-bearer-and the standard just happens to be the symbol of the SQ. However, he then ends up in the path of hot wax, poured over the Vikings by the Parisians, and is believed to be dead by the other three, while in reality he is alive and returns to the Viking camp. The next day, Dak volunteers to be part of the group to send burning boats to the bridge, in an attempt to get back the SQuare.. He succeeds and sabatoges the boats, so they don't destroy the bridge, but is caught by Gorm, a Viking who is part of the SQ.
Back in Paris, Riq and Sera crack on of the SQuare's codes, which Sera had memorized: Ensure Siegfried Takes Paris Peacefully. Back in the Viking camp, Dak is freed by Rollo, whose ancestor met a Hystorian and taught Rollo that the SQ isn't good (although Rollo isn't a part of either group). To reunite Dak with Riq, Sera, and Bill, he dresses as a berserkr and joins the beserkergang. He meets up with the others, along with Rollo, who assures them that he can handle the situation from there, so Dak, Sera, and Riq warp to 1814 just as Bill, who Sera was developing a crush on, is shot with an arrow. Vígi joins the trio, however, so they teleport to a place where Dak knows Rollo would be-celebrating a victorious battle. Due to what they changed in 885, however, Rollo lost the battle, and is surrounded, and if the enemies don't back off, Rollo will be unable to stop Siegfried from conquering Normandy and therefore continuing the break. Dak, Sera, and Riq are able to trick the enemies into thinking they are being attacked, allowing Rollo to stop Siegfried, but Dak, and eventually Sera and Riq as well, is caught by Gorm and leads him to the Viking Camp for information on his parents, but all three are rescued by Vígi.
Sera then has an idea on how to fix the break-instead of preventing the Vikings from conquering Normandy, they simply make sure Rollo, not Siegfried, rules over it. This works out well, and in the festivities, Dak meets with his parents, who are in the same time as him. the trio warp to 1814, but not before Dak shows Sera what his parents gave him-an iron key.