Full Idea
McTaggart's argument is 1) B-series relations are temporal relations, 2) There cannot be temporal relations unless there is change, 3) There cannot be change unless there is real A-series ordering, so there can't be a B-series unless there is an A-series.
Gist of Idea
The B-series must depend on the A-series, because change must be explained
Source
report of J.M.E. McTaggart (The Nature of Existence vol.2 [1927], vol.ii) by Robin Le Poidevin - Past, Present and Future of Debate about Tense 1 a
Book Reference
'Questions of Time and Tense', ed/tr. Le Poidevin,R [OUP 2002], p.16