In “What Lies Tangled,” an eminent mathematician is killed in a gruesome bomb attack, leaving Lewis and Hathaway to quickly discover that the victim had many enemies — several of whom could have killed him. When another bomb is discovered at the home of the victim’s brother, the case moves in another direction. Then a chemistry professor is murdered, and a clue is uncovered that helps solve the case. Meanwhile, Lewis’ long-planned trip with his girlfriend (Clare Holman) is put in jeopardy as Lewis worries about whether his job will be waiting for him when he returns.