The British mystery show "Rosemary and Thyme" does not have a fourth season. The main characters in previous seasons were Rosemary Boxer, played by Felicity Kendal, and Laura Thyme, played by Pam Ferris.
The show is based on the two main characters, who are gardeners, being pulled into solving strange crimes. The two women meet up and plan to work together as gardeners, but over hearing things as they work leads to them looking at clues and trying to solve the case that they stumbled across. Thyme is actually an ex-police officer while Rosemary is a university lecturer in horticulture. The first season was six episodes, while the last two seasons had eight episodes each.