Get on train.

The man watches in despair as you blank him and board the train into an empty carriage. He glances over to his left, where the sound of running footsteps was coming from, then his expression changes to one of horror.

Just as the doors close, he tosses the painting onto the train. "Take it to Aveugle", he shouts, "for pity's sake!".

You can:

Take a quick peek at the painting.

Leave the painting on the floor. If anyone asks, it's nothing to do with you.

Pick up the painting and hide it behind your back. Whoever was after it might have got onto the train too.