Glassmaker's Apprentice (Hearts of Amaranth #3‪)‬

Kait Selias remembers nothing about her past or the events that turned her and six others into immortal beings known as the Gospels. But a dark history connects the immortals, binding them together in an eternal war between Chaos and Order. When Kait receives the journal of Katrina Selias, she begins to piece together the shards of her broken past.

In 1803, Katrina arrives in the Siberian town of Kurgan to investigate a series of bizarre murders gripping its icy streets. A masked killer stalks the marketplace, kidnapping his victims and forcing them to take their own lives. While searching for the perpetrator of the ghastly events of Kurgan, Katrina forms a relationship with a mysterious stranger named Marius Laurent: the glassmaker's apprentice.