Immensely imaginative, but dragged down by its pacing. Too quick, too much info in a small amount of time. Even then, the acting was amazing, the characters very compelling and I love that the Doctor's race is once again front and center as the episode tackles this topic wonderfully.

Oh, and my jaw dropped at THAT appearance (I actually rewinded the episode 10 seconds  as I thought I was hallucinating)

Get this writer back!

Edit: so there was another mad appearance that I instantly recognised and I can't tell where it is going but I'm excited, it's Captain Poppy!