After the global warming came the Great Thaw. Following that came the Ark, whose new governor wants to prohibit speech for ever. Mair is a Word Crafter, and her work is to keep words alive. In the shadows of the trees, she and the other crafters teach the children about language, music and art.

Wedi'r cynhesu byd eang daeth y Toddi Mawr. Wedyn, daeth yr Arch. Mae rheolwr newydd yr Arch eisiau gwahardd siarad am byth. Ond Crefftwr Geiriau ydi Mair, a'i gwaith yw cadw'r geiriau'n fyw. Yng nghysgodion y coed, mae hi a'r crefftwyr eraill yn dysgu'r plant am iaith, cerddoriaeth a chelf.