I call it the "sort-of" HQ because they don't really have an office. ActionStation exists in what old farts like me call cyberspace, but which is probably now called something like "the digital realm".
It had come to my attention because I had clicked the "act now" button in an online discussion of some issue I felt strongly about. Now I'm on their email list. And I felt moved to find out who the people were behind the year-old group and what made them tick.
The office session was a strategy meeting being conducted online with other group members in Wellington and San Francisco. On the agenda was how they would respond to John Key and his Trade Minister Tim Groser dismissing them as "rent-a-crowd" stirrers for calling for the text of the TPP to be made public (presumably the 26,330 signatories to the petition were the crowd being rented). The discussion was urgent, intense and impressively focused.
The same intensity was on show the day before when, in a sundrenched St Kevin's Arcade cafe, the pair explained to me the essence of ActionStation's "open model" approach to campaign.
Focusing on domestic issues (Campbell Live and child poverty were big this year), the campaigns are member-led, O'Connell-Rapira told me. "We ask members what they care about and run with issues based on where the energy is. We observe what is happening in the media and what is capturing people's attention, and we seek to capture that energy."
Mearns, 22, and O'Connell-Rapira, 26, offer a robust rebuttal to people of my generation who marched in the streets to stop Springbok tours and visits by nuclear-armed warships or demand homosexual and abortion law reform and who are inclined to think that this generation of young people don't give a damn.
But asking why the kids aren't on the street is the wrong question, Mearns suggests. "In this age, we are online and we are talking about creating change, but nobody is seeing what we are talking about.
"In your generation, there was a really stark difference between what we were changing from and what we were changing to. We live in a globalised world and so we are campaigning for what the future should be, rather than stopping what is currently happening."
O'Connell-Rapira, who worked on the Rock Enrol campaigns to get young people to enrol and vote in elections, says young people "care a lot and the things that they care about they care very deeply about".
"We have a challenge in breaking through the noise because the political process is not occurring in the channels in which young people are engaging. Because we are online, on platforms on Facebook and YouTube and we will use WhatsApp and Snapchat which is meeting young people in the places that they are."
I can't help pointing out to them that, last time I looked, Campbell Live was still dead, child poverty was grotesquely alive and there was no sign that the Government was going to publish the text of the proposed TPP any time soon. Are they in danger, I ask, of becoming part of the social wallpaper - the country's pet malcontents who don't actually change anything. But, they counter, political and social change is a long game.
"We are trying to capture the widest group of people possible," says O'Connell-Rapira. "You can only create change if the decision-makers you are trying to influence have something to lose by their constituents not supporting them.
"Hopefully, eventually, we will pull in enough people that they will have to listen to us, because there will be a political or financial cost to their not doing so."