The Gods of Mars left off, Warlord finds John Carter roaming the lands of the First Born with Woola by his side, hunting down pockets of Thern resistance and seeking a means to free Dejah Thoris, Thuvia and Phaidor from the Prison of the Sun - and most importantly, learn if Phaidor managed to kill Dejah Thoris in there or not.
He luckily chances on two of his enemies, the Holy Thern Matai Shang and the black Prince Thurid as they are openly conspiring to open the Temple of the Sun and take the three women to a place where the Therns' power remains strong. He follows them, seeking an opportunity to slay them and rescue his wife, but a wrong turn in the winding cavern tunnels under the Sea of Korus delays him long enough for Thurid and Matai Shang to kidnap the women and flee to a waiting flier.
John Carter gives chase, but his flier is shot down over the Forest of Kaol, on the Martian equator in the opposite hemisphere from Helium. After a fight with a vicious hornet-like monster called a sith (likely the source of George Lucas' use of the word), he makes his way to the City of Kaol, one of the regions still faithful to the Thern religion, where Matai Shang and Thurid have been given sanctuary by the local Jeddak. Just as John Carter is about to be put to death for blasphemy, he's rescued by a friend of Kaol's Jeddak - Thuvan Dihn, Jeddak of Ptarth and father of Thuvia. When Matai Shang flees rather than produce the "slave girls" who are Dejah Thoris and Thuvia, Carter and Thuvan Dihn take off in pursuit.
Their pursuit takes them all the way to Mars' forbidding North Polar region, long known as a forbidden zone due to the fact that ships flying above a certain latitude never return. Here they find the buried hothouse cities of the Yellow Men, a race long believed extinct. Here Carter must contend not only with the cruel Thern and the lustful black prince, but with the savage appetites of Sallensus Oll, Jeddak of the North and his vicious pet apts - one of the most terrifying predators on all of Barsoom.
This book rounds out the initial trilogy of Barsoom tales, and ends on a note that could conclude the entire series well enough if Burroughs had decided not to continue. It is also a fantastic example of some of the tools Burroughs used to keep a story moving that would probably get him labeled a poor writer today.
Burroughs is a big fan of the lucky coincidence and there's a couple big examples on display in this volume - for example, John Carter and Thuvan Dihn need to pass through the "Carrion Caves," a tunnel complex filled with rotting corpses and prowled by the royal apts to deter any who would try to enter the land of the Yellow Men this way. There is apparently one day every month where the apts gather in one cave and sleep for a full day. Guess which day it is when John Carter and Thuvan Dihn are passing through? Or, later on, while escaping from the dungeons of Sallensus Oll, John Carter's route to freedom takes him right up to the door behind which Thurid is loudly plotting to betray Matai Shang with the help of the man who controls the giant electromagnet used to destroy ships flying too close to the lands of the Yellow Men.
Likewise, Burroughs is a big fan of forcibly separating his characters and then reuniting them later to drive story. The main through-plot of this novel and its predecessor is that John Carter has been separated from Dejah Thoris. Burroughs keeps letting the two lovers see each other briefly, just enough to let them know the other is still alive, Similarly, while Carter and Thuvan Dihn enter the city of Kadabra together they are quickly separated. This makes for great story-telling because it leaves Carter to rely on himself to get himself out of scrapes, but after a while it makes you wonder why John Carter bothers with traveling companions at all.
The one big disappointment I had was how it wrapped up the John Carter-Dejah Thoris-Phaidor love triangle plot (is it a triangle if one of the lines of connection is "kill" and another is "keep from murdering my wife"?). Phaidor throws a cruel laugh at John Carter as she's leaving Sallensus Oll's throne room, having seen that Thurid kidnapped Dejah Thoris while (literally) John Carter's back was turned. Then, on the flier as Thurid, Phaidor and Matai Shang are making their escape with Dejah Thoris while John Carter dangles from a rope below the ship, tables are turned. Thurid stabs Matai Shang and throws him overboard to lighten the ship, and just as he's about to send John Carter to a similar fate, Phaidor jumps up and stabs Thurid repeatedly, stating first "this is for Matai Shang!" and second "this is for Dejah Thoris and John Carter!"
She explains, after Thurid's corpse has been disposed of, that she realized the error of her ways and understands the purity of love that John Carter and Dejah Thoris share versus the petty jealousy and possessiveness with which she approached "loving" John Carter. She makes a comment about reparations for her sins, and then throws herself over the side!
I kind of think she's overstating her case on learning her lesson, given the "cruel laugh" she throws in Carter's face barely an hour before. I feel like she killed Thurid to avenge her father, and threw herself over the side knowing that with Matai Shang dead, the power of the Therns was truly broken. The bit about learning her lesson regarding love seems like rationalization to me.
The novel ends on a high note with John Carter and Dejah Thoris being reunited, with their son Carthoris falling in love with Thuvia of Ptarth, and the charges of heresy against John Carter dropped to the thunderous applause of Martians from pole to pole. And I think this is a great place for me to take a little break from Barsoom and read something else briefly before returning to that world of barbaric splendor.