liz: erica, thanks for inviting me to your birthday party. i was really looking forward to next saturday night, ...
erica: i've been planning this party for ages! you're coming, aren't you?
liz: well, erica, i'm calling you up to explain. unfortunately i'm not going to be able to make it.
erica: no way! i refuse to accept that. i insist on your coming.
liz: i'm sorry, i really am. you see, it's my parents' wedding anniversary, and they're having the whole family over for dinner. they expect me to be there, and i can't let them down.
erica: so, sneak out as soon as the dinner's over.
liz: i can't just walk out like that.
erica: of course you can.