What are the things?

In Chapter Ten, Calvin, Meg, and Mr. Murry see three grey figures moving across the field towards them. They seem like animals, except they walk upright. When they approach, Meg sees that they have not real faces, just tentacles coming out of their furry bodies. Meg begins to think that her father has killed them all by bringing them here. The creatures ask them what they are doing, and as Calvin tries to explain that Meg is hurt, one of the creatures reaches out to touch her with its tentacle. Soon, it picks up Meg and cradles her and tells Mr. Murry that it is taking her away.