Brake lights don't work

SOURCE: no turn signals or brake lights

try turning the hazards on and off several times these switches go bad and will keep the lights from coming on

SOURCE: turn signals dont work brake lights dont work

You didn't mention your rear brake lights. If they don't work either then you probably have a bad light control module (LCM). This is a common problem with big Fords. You can buy a replacement part ($250) or have yours rebuilt (www.autoecu.com). The module is located under the dash to the right of the steering column and is fairly easy to replace.
Do the turn signals work? If not it may be the turn signal switch. The aftermarket parts are cheaper than a Ford factory part; check the guarantee before deciding.
Worse case scenario? You need both parts.

SOURCE: 1998 Mystique brake lights don't work while the window brake light does work.

Try a continuity test, not sure where to find the electrical scheme but if you obtain it, use a tester or borrow one to test the continuity of the wires of both taillights, could be simple as a cut wire.

SOURCE: Brake lights not working. bulbs are good. brake

better get a second look at the brake light switch, there might be two, third brake light is on a different circuit, switch light circuit goes to signal switch then brake lights

SOURCE: where is the turn signal flasher and brake light module

might be an inline fuse