Prerequisites: A basic knowledge of who River Song is would be enough here.

The Unknown is a competent, if unexceptional, opener to this boxset. The central premise here is surprisingly engaging, and while its execution isn't anything to write home about, it's dealt with in a fun enough manner that I was relatively satisfied. Notably, I think it was the right call to have River and the Seventh Doctor suffer from mutual amnesia for most of the story. Unlike with the Eighth Doctor, I legitimately can't imagine River flirting with McCoy in an unawkward manner, and this seems to be pretty much the best solution.