Need help with trip from Bayeux to Mürren

Yes, all train is our preference over train-fly-train. You'll need several connections either way, including crossing between Paris by taxi (recommended for a party of 4) between Paris Gare St. Lazare and Paris Gare de Lyon.

You must not miss the reserved train departing Paris. The French tickets have discounts if you lock them in now but the Swiss tickets don't, as well as the Swiss tickets don't need time or seat reservations. You can also consider a Swiss Travel Pass for 4 consecutive days ($266 per adult) which would kick in from Basel (the fastest crossing point) or any other border.

How to Look Up Train Schedules and Routes Online gives you the DB train schedule link and tips for using it, but does not sell tickets. It will show you the entire schedule from Bayeux to Muerren (by either one of two routes from Lauterbrunnen). If you have Rick's Switzerland, book, see those on the maps on p. 128-9. Muerren BLM is a bit shorter ride for this 10-hour travel day.

Thanks Laura..you wouldnt just take the metro between train stations?

April, have you ever been in the Paris Metro with luggage? It can be VERY unpleasant.

I've taken the Paris Metro several times with my luggage as a single traveler, but this route involves a metro connection and four people sharing a taxi seems like a good deal; might cost €15.

Yes, Laura, I've taken the metro also...and since the OP seems like a rather inexperienced traveler I would not recommend metro plus luggage.

April,

I agree that travel by train is the best option in this case, especially for a party of four. It will be a long travel day though. Although It means an early start, you might consider a departure from Bayeux at 06:43, as that's one of the shortest trips and will get you to Mürren at a reasonable hour.

I also agree that Taxi from Gare St. Lazare to Gare de Lyon is probably the best idea. If you use the train listed above, you'll be arriving in Paris at 09:00 and hopefully the traffic won't be too thick. As a solo traveller, I've used the Metro many times for transfers like that, but with four people a Taxi will be easier.

"From Interlaken is it a train or tram to Mürren?"

From Interlaken Ost (there are two stations in Interlaken), you'll transfer to the Berner Oberland-bahn for the short 20 minute trip to Lauterbrunnen. Be sure to note the destination on the side of the car, as some trains split in Zweilütschinen. When you arrive in Lauterbrunnen, walk across the street to the cable car station, walk up the stairs and board the next cable car, which will take you to Grütschalp. When you arrive there, board the small mountain railway, which will be waiting with usual Swiss efficiency. In about 20 minutes, you'll arrive in Mürren.

There is another route to Mürren via the Schilthornbahn, but the method suggested above is the quickest and easiest (especially after a LONG travel day). Once you reach Mürren, you can relax over a glass of wine and enjoy the ambiance!

I wouldn't suggest being "pokey" in Switzerland, as the trains are very precise and they wait for no one!!!