Bethesda recently announced that they're going to release a free trial for Dishonored 2 on April 6. Available for PS4, Xbox One, and PC, the trial will allow players to access the first three missions of the campaign as the supernatural assassin of their choice—Empress Emily Kaldwin or the Royal Protector Corvo Attano.
If you haven't played the DLC for the first Dishonored (available separately or through the Definitive Edition), I'll be vague. A familiar mad witch seizes the throne and leaves the empire in chaos, and armed with the tools of either Corvo or Emily—while their skill sets are different, both have their merits—you must travel beyond Dunwall to Karnaca in an effort to restore power to the right hands. (However, the devs did recommend that you play through the DLC of the first game prior to beginning the second one, so if you have access to that then I'd say go for it. If not, no worries; it isn't like you're missing out on absolutely vital information.)
The free trial can be downloaded from the PSN Store, Xbox Marketplace, and Steam. But never fear; if you decide to upgrade to the full game at any point, you'll retain all saves made during the trial. So go forth fearless on April 6, your Mark of the Outsider held at the ready.