Ace Returns! was an online special, which served as part of the promotional campaign for the blu-ray box set of Season 26 of Doctor Who. It included the narrative minisode WC: The Promise as well as a trailer for the box-set.
Like Jo Grant Returns before it, this was a narrative trailer, set around the present day, featuring a companion from the season who has now long since departed the Doctor's company. However, due to this Wiki choosing not to consider trailers and commercials, narrative or otherwise, to be full in-universe sources in their own right, this story is not currently considered valid by this Wiki.