Archer to transfer his katra. After burying him, a focused Archer leads T'Pol directly to the concealed T'Karath Sanctuary, where they are quickly captured. Back on Enterprise, Doctor Phlox discovers that the DNA was planted. Commander Tucker and he then examine security scans near a checkpoint in the embassy and single out a hooded man holding a suspicious package. Furthermore, they notice that the guard at the checkpoint seems to already know who the bomber is. Unfortunately, the guard is in a coma from the blast, and Archer and T'Pol are incommunicado. Though it violates standard Vulcan ethics, Phlox and Tucker consider a mind meld, and Soval decides to perform it himself. To his surprise, he discovers that the suspect is Stel, a Vulcan investigator attached to V'Las. Soval then resolves to inform the High Command. Production Production on the episode began on September 14, 2004, and ran through to September 22. The standing sets were used for the first three days of filming. Further sets were created to represent the Vulcan Embassy and portions of the Forge. The final two days were filmed on site in Simi Valley in southern California, which doubled as the main areas of the Forge. The property used in the valley was owned by mining company P.W. Gillibrand, which was near property owned by Vulcan Materials Company. Optical effects were added to represent the firestorm and the sehlat. The CGI sehlat was based on one which previously appeared in Star Trek: The Animated Series episode "Yesteryear". Visual effects producer Dan Curry said that the team "looked at the animated series and it just looked nice and pleasant, so I did a couple of sketches to do a reinterpretation of it to make it look scary, but not be too radical a departure from the original". Eden FX modelled the CGI under supervision by staff visual effects supervisor Art Codron. Additional care was taken to create the fur so that close-ups could be used if required. The only physical portion of the sehlat to be created was a single paw. "Yesteryear" was set in the Vulcan city Shi'Khar, which reappears in "The Forge", and it is also the first mention of the area on Vulcan called the Forge. A further reference was made to "Vulcan's Forge" in the Deep Space Nine episode "Change of Heart". "The Forge" and the following two episodes make reference to