Flotsam (Thomas) is the daughter and helper of crusty old lighthouse keeper Joe Clark (Edward Ellis, in fine form). The reason why Clark lives 'out yonder' is because he's a fugitive from justice: years ago, he killed a man under complicated circumstances. Clark's official assistant is Amos Bart, but Flotsam does much of the work of maintaining the lighthouse.
This isn't one of Olive Thomas' "baby vamp" roles, which she was mostly known and loved for. This is Olive in a sweet, wholesome, loving daughter role, which she's wonderful at. The story, which I found a perfectly fine one, could have used a little more fluffing up, and so this film could actually have benefitted from being a little longer. But Olive herself is delightful, as usual.