Lansbury, back on the case

Seven years ago this month, it looked as if Jessica Fletcher had finally solved her last case. The elegant lead character of “Murder, She Wrote,” the longest-running detective drama in television history, had spent the previous dozen years untangling crimes while traveling the country promoting her popular series of mystery novels. But with more than 250 episodes in the can, series star Angela Lansbury appeared ready to ease Jessica into retirement.

Make that semiretirement. Tonight at 9 on CBS, Lansbury proves there’s life in the old girl yet with the fourth TV movie of the “Murder” franchise, a diverting two-hour whodunit titled “The Celtic Riddle.”

Lansbury, who will be 78 in October, returns with her cool and classy brand of charm intact in a story that has Jessica being summoned to Ireland for the reading of a will. It seems Jessica crossed paths with the deceased many years back, intervening in his attempted suicide and helping him to realize that there was much yet to live for.

For her kindness, Eamon Byrne (Peter Donat) left her a simple but lovely cottage within the family compound, which doesn’t endear her to some of the greedier members of the clan.

Eamon also gave each of the beneficiaries an envelope containing a clue to the biggest prize of the estate, identified only as “a treasure of estimable value.” In a final videotaped message delivered from his deathbed, Eamon tells everyone that they need to work together to solve the riddle. That’s about the time people begin dropping like flies and Jessica shifts into full sleuthing -- and survival -- mode.

Lansbury, who has four Tonys to her credit, has been nominated for more than a dozen Emmys without a win. But with the actress continuing to churn out these light, enjoyable mysteries, her case remains open.