All of Mars is united under John Carter, but forces behind the scenes are plotting to tear the Red Planet apart. A conspiracy threatens to trigger all-out war between the Red Martians and the savage Green hordes - can Carter's most steadfast ally, the mighty Tars Tarkas, overcome his own bestial urges and save the planet? Meanwhile, a beloved figure from Mars's past makes a surprise reappearance, but all is not well, and soon Carter and his family...