Plot-wise, a 3.5/5, but the unique atmosphere earns it another half star. The first episode in particular is spellbinding as the Doctor finds himself at a cabaret club in 1930s Berlin. My only previous Iris experiences were in the Excelis saga where I found her quite annoying honestly. Hear she's used in smaller doses and fits the overall vibe of the story. I wasn't expected the twist that this was Iris' Valeyard story. It was a bit hard to keep up with the exact machinations of everything, but the frame narrative and overall vibes were sublime. Fun listen after the Iris/6 reunion 22 years on was announced recently.