What Was in the Bag?

I think it was drugs. Just prior to getting off the train he went into the bathroom and took something white and in small sealed bags/packets out from beneath the sink and put it in his carry-on bag.

I'm no expert, but . . . .

Drugs. Thomas was a drug currier & a low life, in general.

I fail to see how anyone couldn't understand what is in that bag.

Of Course It's Drugs!!!

You see the plastic baggies with the white powder inside of them when Thomas opens the brown paper bag in the bathroom on the train.

Then you see Thomas hide that same brown paper bag in the hole under the roof of the hotel.

Then you see Thomas try to retrieve the same brown paper bag from the hole in the roof while it's raining, and the film clearly shows that the rain saturated the paper bag, and its contents, and you then see the rain washing away the white gooey stuff, the rain soaked drugs down the roof.

Why else do you think that Thomas was then always on the run for the rest of the film, stopping only for a while at the house of Lewis and Elizabeth in England? The film clearly shows that Thomas was on the run because he failed to deliver a valuable smuggled shipment of drugs and the drug dealers that he was working for were after him.

Furthermore, it's apparent to me that Thomas used that hole under the roof of the hotel in Baden Baden to hide drugs in the past, because he doesn't go looking for a suitable hiding place, but instead makes a bee line straight to that obscure hiding place on the roof. So it's verily likely that knew already knew about it and used it previously to hide drugs.