Is there a plausible mechanism behind the Casimir effect?

Yes, that space is filled with something, because you are not going to get those two plates reacting against one another unless there is something there that transmits the energy. It is not air, because all the air is taken out in the vacuum, and yet the experiments that take the air out end up showing us that something is there, otherwise there would be no transfer between the plates. They perfected the Casimir experiment and got the same effect, so something is carrying that energy, and if that is the case then space is not empty, space is filled, as they are now finding out in quantum mechanics. I have quoted Robert Laughlin, the Nobel laureate in physics, many times; he says space is filled, more like window glass than empty space, and that we can go in there and take out a part, and if our instruments react to whatever is there, then we know something is there. So the universe is more like a bowling ball than a balloon; we just cannot sense it with our limited senses and instruments, because the particles they are talking about in quantum mechanics are incredibly small, on the order of ten to the minus thirty-five meters. These are the last pieces of the puzzle coming together.