Having defeated the forces of the Emerald Claw and the Shrouds, the heroes return to the House Tharashk Refinery to find almost all of its workers and staff struck down by the illness that afflicts the Silver Flame’s congregation. The sufferers writhe and gibber, raving about eyes and darkness, begging their attendants to cut off their limbs and occasionally shouting out numbers – numbers that slowly but constantly increase. Ash attempts to make sense of their ravings – as does Spark, who fears that this sickness could afflict even warforged. Sláine checks this by speaking to the Refinery’s few warforged workers, while Rufus tends the sick and Kaddik speaks to the Refinery’s sentries. Amidst all this, Caleb tries to glean the secrets of the helm of seven deaths, but it defies his magical skills.

Eventually the heroes work out that something has infected the Refinery’s water supplies – or, more accurately, the water flowing down the Koronoo River to Stormreach. Rufus uses an alchemical reagent to purify the Refinery’s well, and the contaminants reveal themselves – insubstantial flakes of telepathic infection, like broken insect wings, that form a clump like a slab of rotten ice and then dissolve in the sunlight. Durgran’Torrn sends the heroes to get a barge from Surrinek’s Riverboats in Oldgate and head up-river to stop the infection, which likely is the work of the Storm Hammers. All but Rufus head off; he stays behind to minister to the infected.

The heroes pilot the barge upriver, passing clump after clump of infected thought bobbing down to the city. At one point a fallen tree blocks the river; when clearing it, they are attacked by fell taints and two Storm Hammer cultists, twisted men who speak in eerie unison and tell the heroes that they were expected. After defeating the Hammers, the heroes continue further upriver until the Koronoo flows through ancient and massive giant ruins, where they find the source of the mind-disease – Telos, an agent of the Hammers, and a huge fell taint called the Scourge of Thought (plus a hivemind of telepathically-corrupted alligators). In a hard-fought battle they defeat the enemy, but the Scourge’s death throes momentarily connect their minds – and let loose a handful of telepathic spores into their consciousnesses.

The Storm Hammers have been stopped once again – but at what cost?