It's chaos aboard Presley Station, as the corrupted Shan'tee - conceptual beings from a different order of reality - prey on the human colonists, while on the gas giant below, vast storms conjure up winds of horrifying speed that threaten to tear the Station apart! Caught in the middle of the chaos: the Doctor and Gabby! Can the Doctor find the counter-melody that brings peace back to the Station? And can the ever-humming Gabby keep herself from singing to stop her mind being invaded by a sentient song? Meanwhile, back on Earth, Cindy makes up her mind. And in deep space, an old face comes calling!