Complex sentence: Pearce falls fatally ill with consumption, and while Merivel is tending to his dying friend, they then discover that Katherine is pregnant with Merivel's child, and after the death of Pearce, Merivel and Katherine leave.
Split into simpler sentences: Pearce falls fatally ill with consumption, and while Merivel is tending to his dying friend. They then discover that Katherine is pregnant with Merivel's child, and after the death of Pearce, Merivel and Katherine leave.