Widow Lucy Carmichael raises her children and shares her home with divorcee friend Vivien.
The original premise of the series was that widow Lucy Carmichael lives in the fictional town of Danfield, New York, with her teenage daughter Chris and younger son Jerry, with her divorced friend Vivian “Viv” Bagley and Bagley’s young son Sherman as tenants. Early episodes included their next-door neighbor, Harry Connors. Lucy’s late husband left her a substantial trust fund, managed by a local banker (originally recurring character Mr. Barnsdahl, and later regular character Mr. Mooney); Lucy would frequently try to persuade the bank to let her raid the fund for various purchases or harebrained projects. Lucy also took on various jobs to boost her finances. Lucy, Viv, and Chris all dated regularly, yielding additional fodder for plots; in early episodes, Viv had a regular boyfriend, Eddie Collins.
In 1965, the show was extensively retooled for its fourth season. Lucy moves to Los Angeles to be closer to Chris, who was attending college in California (but no longer appeared on the show), and enrolls Jerry in a military boarding school there (facilitating his also being written out). Viv, now remarried as Vivian Bunson, remains in Danfield with Sherman, but visits Lucy a few times; Lucy’s new best friend is Mary Jane Lewis. Lucy finds that Mr. Mooney has been transferred to the Los Angeles branch of the bank, and she eventually becomes his employee there. The new setting provided ample opportunity for celebrities to appear as themselves, often becoming entangled in Lucy’s zany schemes. References to Lucy’s children and her trust fund were eventually dropped, and this remained the show’s premise through the sixth and final season.