Doctor Who: The Ninth Doctor #6

After a brief break in New York City, the Doctor and Gabby were ready to set off in search of a new adventure - but trouble is never far from the Doctor. Picking up a mysterious signal in the heart of Manhattan, he discovered a secret action where, among the junk, he found something of true value: an alien device with unknown and powerful properties! Purchased by a private bidder, the Doctor followed its signal to actress Dorothy Bell's apartment - stalked by the street-smart agent, Cleo! Having got her hands on the device at Bell's home, Cleo revealed the device's true power: reverting Dorothy's assistant Vivian back to a baby! The Doctor was a hit too... and is retro-regenerating back to his ninth incarnation!