Doom Coalition was an edgy four boxset storyarc so-called "four boxset storyarc". It was heavily advertised as 16 stories all planned as a continuous and complete series, in contrast with things like Dark Eyes or NuWho where there was no big plan from the start. However, Doom Coalition effectively doesn't end, it trails off into unresolved plot points and cliffhangers. So we'll be stuck with another whole new boxset of Helen sometime. Hooray...