I had to take the RER D from Gare de Lyon (GDL) connecting to RER B for an early flight out of CDG, needing to arrive at CDG at 6:30 am. I felt unsafe at GDL as it was fairly empty at 5:15 am. The platform itself was almost vacant. I took to standing next to the alarm button. I was approached by a young male with a story about putting his phone down and now it was gone and could I call it so he could locate it? Made no sense. I said no and my phone stayed safely stowed in my bag. A would be scam. I waited on the platform with green signage indicating RER D to no avail, with one arriving train and no departing train, only to discover that I needed to descend another flight of stairs that displayed in huge letters RER A in red - to arrive at the departing RER D. No idea how I would’ve known this. An unpleasant experience. I also have heard from others that this platform is “lonely” and prone to thievery. This was the only time I felt unsafe on my vacation.