Employer Changing the Game

Hi, all.  Have a work question -- wondering if anyone knows the "rules" or has been through something similar.  I did leave this in the Working Moms group as well, so apologies if this is duplicate for anyone...

My employer required a written, approved maternity plan before I went on leave. The plan, which they signed off on, specified that upon returning full time I would come into the office two days a week and work from home the remaining three.  Additionally, my hours would flex slightly for an earlier start and departure time so as to make daycare viable (normal hours are 9-5:30 -- flexed hours include me starting early to leave at 4:15 p.m. -- but still putting in at least 8 hours a day).  My commute to the office is an hour each way and my husband travels weekly for his job, so daycare dropoff/pickup is all on me...

All of this said, they changed my boss my second week back (currently on PT for another 1.5 weeks).  Last Thursday my boss made comments over the phone about concerns with my new arrangement -- even though there have not been any performance issues.  Then yesterday she requested I come into the office today/tomorrow for an in-person meeting with the owner of the company -- who, according to last Thursday's discussion, is the one with concerns.

If they pull the flexed hours and/or work from home, there is no way I can continue working there given daycare hours and my commute time.  I'm of course upset -- I've worked there for more than five years and killed it in the past with 50-60 hour work weeks.  I get that that isn't happening now, but it wouldn't be happening regardless -- I have a new baby...

Has anyone had something similar? How did things turn out?