In the end it took three people to get them together. Juliet convinced Gus to help who in turn, by some miracle, convinced Henry. There was a long and complicated plan that, once the planning was done, took a full day to complete. In the end both Lassiter and Shawn ended up locked in an interrogation room. Trust me, it was harder than it seems. But it all paid out because in the end they were together. One may have gotten a black eye also, but it'd take a long time to explain everything that happened in those two hours.