Murder in Edinburgh — D-L Nelson

Annie Young-Perret goes undercover at the Edinburgh, Scotland office of a multi-national insurance company to investigate the suspicious hit-and-run death of her school friend Chantal's husband, Duncan.
Meantime, other company employees are murdered in Boston, Colorado Springs and Saint Petersburg, Russia by a serial killer who delights in finding original ways to kill her victims.
Joining the search are Annie's retired French police chief husband, Roger; a writer from the new Early Scottish Poets Museum for which Chantal is curator; a coworker of Duncan's; and two off-duty Edinburgh police.
When the insurance company CEO learns of their inquiries, he orders a contract on a new target.