Pope Francis is known for his symbolic gestures, but his visit to a Greek refugee detention centre as the EU implements a controversial deportation plan is as provocative as any he has undertaken.
Francis and the spiritual leader of the world's Orthodox Christians will spend nearly an hour on Saturday greeting some 250 refugees stuck on the Greek island of Lesbos.
They will lunch with eight of them to hear their stories of fleeing war, conflict and poverty and hopes for a better life in Europe. And they will toss floral wreathes into the sea to pray for those who never made it.
It is a gesture Francis first made when he visited the Italian island of Lampedusa in the summer of 2013, his first trip outside Rome as pope, after a dozen migrants died trying to reach the southern tip of Europe.
Refugees are not numbers, they are people who have faces, names, stories, and need to be treated as such.— Pope Francis (@Pontifex) April 16, 2016
He made a similar gesture more recently at the US-Mexican border, laying a bouquet of flowers next to a large crucifix at the Ciudad Juarez border crossing in memory of migrants who died trying to reach the United States.
The Vatican insists Saturday's visit is purely humanitarian and religious in nature, not political or a "direct" criticism of the EU plan.
But spokesman the Rev Federico Lombardi told reporters Francis' position on Europe's "moral obligation" to welcome refugees is well-known, and that the EU-Turkey deportation deal certainly has "consequences on the situation of the people involved".
The Vatican official in charge of migrants, Cardinal Antonio Maria Veglio, was even more explicit, saying the EU-Turkey plan essentially treats migrants as merchandise that can be traded back and forth and does not recognise their inherent dignity as human beings.
The March 18 EU-Turkey deal stipulates that anyone arriving clandestinely on Greek islands on or after March 20 will be returned to Turkey unless they successfully apply for asylum in Greece.
For every Syrian sent back, the EU will take another Syrian directly from Turkey for resettlement in Europe. In return, Turkey was granted concessions including billions of euro to deal with the more than 2.7 million Syrian refugees living there, and a speeding up of its stalled accession talks with the EU.
Human rights groups have denounced the deal as an abdication of Europe's obligations to grant protection to asylum-seekers.
The son of Italian immigrants to Argentina, Francis has made the plight of refugees, the poor and downtrodden the focus of his ministry as pope, denouncing the "globalisation of indifference" that the world shows the less fortunate.
Aside from the inherently political nature of the trip, it also has a significant religious dimension.
Francis will be visiting alongside the spiritual leader of the world's 300 million Orthodox Christians, Ecumenical Patriarch Bartholomew, and the head of the Orthodox Church of Greece, Athens Archbishop Ieronymos II.
The European border patrol agency Frontex intercepted a dinghy carrying 41 Syrians and Iraqis off the coast of the Greek island of Lesbos, three hours before the pope was due to land on the island.
The refugees were detained and brought to shore in the port of Mytilene.
Under a controversial European Union-Turkey deal that came into effect March 20, all those arriving on Greek islands from that date on are detained and deported back to Turkey unless they successfully apply for asylum in Greece.
Meanwhile municipal crews are scrubbing walls in the capital and main port of Lesbos after graffiti was sprayed overnight in places where the pope will speak.
The crews removed the words "Papa Don't Preach" sprayed in black at several points on the seafront in Mytilene.