Titus Welliver guest stars in the March 2 episode of NBC's Grimm, which is called "Three Coins In A Fuchsbau." We have no idea what a "fuchsbau" even is, but there you go. It sounds like Welliver might be able to tell Nick a bit more about his Grimm legacy, and this might be a mythology-building episode.
Here's the official description from NBC.
THE SEARCH FOR A MURDER SUSPECT LEADS TO POWERFUL RARE COINS AND ANSWERS TO NICK'S PAST - TITUS WELLIVER GUEST STARS - A failed jewelry store robbery results in a murder that finds Nick (David Giuntoli) and Hank (Russell Hornsby) immersed in a hunt for rare coins. Nick soon learns that these coins have an unsettling effect on whoever possesses them, as Hank and Captain Renard (Sasha Roiz) begin to exhibit unusual behavior. Meanwhile, a mysterious old friend of Aunt Marie's (guest star Titus Welliver, "Lost") comes to Nick with information about his family and what led to his parent's death. Bitsie Tulloch, Silas Weir Mitchell and Reggie Lee.