As the last episode of "Star Trek: The Next Generation" reminded us, all good things must come to an end. For the past six months, Warren Ellis's issues of "Secret Avengers" have been action-packed mash-ups of mad science, superheroics and espionage with a new artist each issue. He's worked with some of the best artists in comics over these six issues and what better way to end than to reunite with his "Nextwave" collaborator Stuart Immonen in the first issue to use the entire six-person team? Things go boom, of course. Who would have it any other way?

A mole in the Office of National Emergency is going to sabotage its storage facilities on behalf of the Shadow Council and the Secret Avengers split into two teams to stop it: one to find the mole and discover what their goal is, and one to prevent the sabotage itself. The two sides demonstrate the two functions of the team with the former operating like an amoral black ops squad set to torture to gain information after breaking in secretly, while the latter is more the typical superhero side of things, rushing into danger, ready to stop whatever is happening. Meanwhile, Beast monitors the situation from the group's headquarters. If any issue of Ellis's "Secret Avengers" has felt like an issue of "Global Frequency," it's this one.

The plot is a great mix of action, intrigue and Ellis further developing the Shadow Council, exploring their relationship to the Cthulu-esque creatures and their larger schemes, all while tying together events from previous issues. The focus on the Shadow Council in this run picked up on one of the more intriguing ideas in Ed Brubaker's run on the title and provides a focus for this group that sets it apart from the regular Avengers.

Ellis spends a lot of time with Steve Rogers in this issue and that depiction is one that could bother some readers. Rogers refusing to torture suspects for information, but allowing Moon Knight and Black Widow to do it instead is a character moment that, no doubt, many will insist is wrong and doesn't seem like something the character would do. Or, it's something that the character shouldn't do. Ellis's time on the title has pushed the characters beyond regular superhero morality and this is another line that's crossed in the process of 'saving the world.' Thematically, it works with the choices the characters have made in previous issues and is one of the central ideas of the run.

On the surface, Stuart Immonen's approach to the art isn't as experimental as some of the artists who have preceded him. He works around a three-tier layout that allows for a lot of flexibility while maintaining strong linear storytelling. It's also a compositional approach that provides a steady rhythm that he can alter depending on the scene. The early interrogation scene packs in a lot of panels to visualize the race against time, while the action scene at the end relaxes a little to spotlight the energy and movement.

"Secret Avengers" #21 is a thematic conclusion to Warren Ellis's six-issue run on the title, bringing together ideas from the previous five issues and using a larger cast. In some ways, it's the issue that best demonstrates Ellis's approach to the title, summing up everything that came before and different types of stories that can be told under the banner "Secret Avengers." And, of course, the art is fantastic. It's a shame to see this run end.