The Triumph of the Sun: Courtney & Ballantyne, Book 12 (Unabridged‪)‬

Menace emanated from them as fiercely as the heat from the sun. Night and day, the drums never stopped, a constant reminder of the mortal threat that hung over them. She could hear them booming across the waters, like the heartbeat of the monster.  

An unimaginable enemy will bring them together.... 

In the burning heat of the Sudanese sun, the city of Khartoum is under siege from the fearsome forces of the Mahdi, the charismatic leader of those who tire of the brutal Egyptian government. In Khartoum, along with thousands of innocent citizens, are trapped the fanatical General Charles Gordon, intrepid soldier Penrod Ballantyne of the 10th Hussars, English trader Ryder Courtney and the British consul and his three beautiful daughters.  

As rescue becomes increasingly unlikely, this group of Queen Victoria's loyal citizens must unite to prepare themselves against a nightmarish enemy, and for the savage battle to survive that must surely follow.... 

The Courtneys meet the Ballantynes in a sweeping adventure.