Catherine Steadman (Jonathan Short/Invision/AP) Published January 03. 2021 12:01AM Moira Macdonald, The Seattle TImes Get the weekly rundown Email* Submit Catherine Steadman’s second career was born on an impossibly hot day in the desert. “All I could think of,” she said, “was the sea.” An actor best known to American audiences as insouciant heiress Mabel Lane Fox on Season 5 of “Downton Abbey,” Steadman was filming the television series “Tutankhamun” in Namibia several years ago — in full Victorian costume, complete with corset. “It was just boiling,” she said, in a telephone interview from her London home. “I thought about going swimming, being by the sea, a cool breeze. I starting thinking about what plot you could get around that setting, if you wanted to read a book.”