Disturbing the dead / Kelley Armstrong.

Enhanced descriptions from Syndetics:

Disturbing the Dead is the latest in a unique series with one foot in the 1860s and the other in the present day. The Rip Through Time crime novels are a genre-blending, atmospheric romp from New York Times bestselling author Kelley Armstrong.

Victorian Scotland is becoming less strange to modern-day homicide detective Mallory Atkinson. Though inhabiting someone else's body will always be unsettling, even if her employers know that she's not actually housemaid Catriona Mitchell, ever since the night both of them were attacked in the same dark alley 150 years apart. Mallory likes her job as assistant to undertaker/medical examiner Dr. Duncan Gray, and is developing true friends--and feelings--in this century.

So, understanding the Victorian fascination with death, Mallory isn't that surprised when she and her friends are invited to a mummy unwrapping at the home of Sir Alastair Christie. When their host is missing when it comes time to unwrap the mummy, Gray and Mallory are asked to step in. And upon closer inspection, it's not a mummy they've unwrapped, but a much more modern body.

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Kirkus Book Review

A time-traveling detective probes the death of a Victorian Egyptologist. The evening gathering at the home of Sir Alastair Christie is surely the talk of Edinburgh. But Mallory Atkinson's interest in the event is more professional than social. Since the 21st-century police detective awoke from a murderous attack to find herself inserted into the body of a 19th-century housemaid working for the Gray family, Mallory has tried ceaselessly to fit into their unconventional Victorian household. Duncan Gray is a doctor who's prohibited from practicing medicine because of his annoying habit of digging up graves, so he's currently serving as the city's undertaker. His oldest sister, Lady Annis Leslie, has been invited to the party Sir Alastair is having to show off his latest find--an Egyptian mummy, which he's planning to unwrap--and she invites Duncan; their sister, Isla; and Mallory to join her. Though, unlike her employers, Mallory knows what's inside a mummy's bandages, she can't pass up the invitation. Alas, the body exposed in the course of unwrapping turns out to be not a long-dead Egyptian, but Sir Alastair himself. It's up to Detective Hugh McCreadie, Dr. Gray's best friend, to find out who switched the ancient corpse for a fresher one. Of course, where Gray and McCreadie go, Mallory is sure to follow. Their investigation is plodding along by the book, at least by Victorian standards--instead of fingerprint or DNA evidence, there's a search for who had access to the mummy and motive to kill Sir Alastair--until the tale takes a sudden turn that puts not only its outcome but Mallory's entire future in doubt. Even time travel has its rules, and here Armstrong seems to be coloring way outside the lines. Copyright (c) Kirkus Reviews, used with permission.