Camille, the blinking question-mark icon usually signifies the startup code can't find your hard-disk. If you have a backup disk drive, then connect it to your computer normally, and power it by its own power-supply. Then restart your computer holding down the "Option" key. You should see all the disk drives the startup code can find. Your hard-disk might be one of them. If you select that, your system might boot. Otherwise, restart again, with the Option key held down, and choose your backup disk drive. That should boot. You would then need to "backup" your backup to your hard-drive, which you may need to rename and/or repair with "Disk Utility" from your currently running backup.
If you don't have a backup disk-drive, restart your computer holding down the "Option" key, and choose whatever disk is found. Good luck