It is before the advent of man, and animals are the dominant species. Jethro is a special mouse: a 'Ticklemouse', but he doesn't kw it yet. What starts off as a relatively simple journey to fetch Nana, his wife Hanna's grandmother, and bring her to their home for the winter, takes many unexpected turns. The adventure really starts when Jethro meets up with Timmo, an ex marine militia sea otter. Timmo is on the trail of the mysterious raiders who - led by the merciless and sinister General Legin - have abducted his family. Together the two must face the perils of the predatory Cats, as well as the Raiders and their Weasel helpers, before Jethro discovers his unexpected heritage and aids the redoubtable Timmo in his attempts to rescue his family and stop the raiders from succeeding in their evil plans.