Blood Ties. Book 4. Fiery Heart

Sydney Sage has to hide too much from her beloved younger sister Zoe, who now works with her. Communication with witches. Personal life. Magical experiments. Zoe is unwaveringly devoted to the alchemists' mission and their authoritative father. If she learns... any of her sister's secrets, she will surely turn away from her. Does Sydney have a chance to show Zoe that life is not limited to blind servitude?
Meanwhile, Adrian performs real miracles with spirit magic – perhaps this will one day help him gain protection from strigoi. But the price for his achievements is getting scarier, so he will have to decide whether his amazing abilities are worth the madness that follows?

The fourth book in the "Blood Ties" series, expanding the legendary universe of "Vampire Academy," in a convenient classic pocket format.
Blood Ties. Book 1. The Princess by Blood
Blood Ties. Book 2. The Golden Lily
Blood Ties. Book 3. Charms of Indigo
Blood Ties. Book 4. Fiery Heart
Blood Ties. Book 5. Silver Shadows
Blood Ties. Book 6. The Ruby Ring