Plot hole: The alien mummy is found by the werewolf in a separate rectangular block of concrete. However, I don't think that the Tennysons would have made the effort of first enclosing the mummy in a separate load of concrete, waiting until the stuff is hard, then putting it into the hole and covering it with a new load of concrete. Too much effort and too little time for one night ("Under Wraps"), since concrete does take time to get hard properly.
Plot hole: When the Corrodium Beam is shut down, there is a brief scene of the sky clearing at Mount Rushmore. But on the cliff face all four heads are seen, whereas the head of Theodore Roosevelt got crumbled in "Secrets," and it's too far forward to have been carved into the mountain face, in place (and same position) of the old head, yet again.