“We are in a war situation and not everyone wants to be visible,” says Ben Cope, ushering us inside.
We’re not in a warzone – but they’re very jittery; fearful of people who don’t share their ambitions and who might sabotage their effort to support the war in Ukraine.
This is Ukraine House – it was established in the Polish capital Warsaw in 2009 to help Ukrainians living in Poland.
A few weeks ago, there were a handful of people working here. But Russia’s invasion of Ukraine has changed all that.
Now, there are lots of volunteers, all busy with Ukraine’s ex-pat war effort – organising aid to be sent into Ukraine and assessing where it’s needed most and how it will get there.
They’re also trying to match refugees with offers from Polish people to take them in. They have filled more than a thousand flats with families so far.
Ben Cope, a Briton, originally from Bedfordshire, and a spokesperson for Ukraine House, talks of “our friends in Kyiv”.
He says: “It feels like what we are doing is what they’re doing – and by trying to be part of that struggle we are really helping people and sending a message we are in this with you.”
Well over a million Ukrainians were working in Poland before the war.
We’ve watched men getting buses at the station – presumably going back to fight.
The operation to strengthen Ukraine’s front lines has taken in foreign fighters.
Now we’ve found refugees also joining the war effort – assisting those foreign fighters to get to Ukraine.
In the arrivals hall at the airport you normally find expectant taxi drivers.
But Yve Tkalenko and Kristina Hai are holding up signs saying “Ukrainian International Legion”.
They have spent hours doing this. Their job, they explain, is to wait for people to come through who’ve signed up to fight.
They don’t have any lists and don’t know who is coming.
But still, the 20-year-olds, who were studying International Relations at Kyiv University, wait – offering any help that’s needed.
Yve says: “I do not want to be the refugee. Unfortunately this happened to my country, but I still might be useful”
And Kristina adds: “We don’t know who we are meeting. We are just waiting for people who want to help our country.”
They point towards a café where they say two men, who are both ex-military and from Georgia and Brazil, are waiting after flying in.
Kristina tells us it makes her feel “really good, we know that we may have some special mission”.
Boxing trainer Sergey is also on a mission – to complete a round-trip drive from Spain to Warsaw and back again with his coach.
He arrived with it packed full of aid and the plan is to take refugees back with him to offer them a place to sit out the war.
Sergey moved to Spain at the aged of ten and has lived there for the past 14 years.
He says: “I have all my family in Kyiv and half my family are in Mariupol – one of the most dangerous zones in the war at the moment.
“I am from Ukraine and I have all my family there – I think all Ukrainians about the world must help each other.”