Various crimes while helping Stefano DiMera
Involved in the conception and hiding of the Gemini twins
Attempted to kill Barb Reiber
In the fall of 1997, John, Hope, Stefano, and Kristen all traveled to a jungle compound where they were introduced to Dr. Rolf, the man working on the cure for Roman. Dr. Rolf recognized Hope, but Stefano managed to warn him not to say anything to Hope. Hope ended up breaking into a storage room, which infuriated him because there were things, including a table, in that room that could jog her memory from the missing four years of her life. Stefano promptly locked the room up with a high tech lock. When Dr. Rolf finally finished the cure, the vial containing the cure was dropped and it was lost. Dr. Rolf and Stefano told John and Hope that the only way to make another cure was for someone to brave the jungle and the natives and retrieve a special orchid. John and Hope volunteered to find the orchid. Hope and John found the orchid and John put it in his backpack, but a native knocked John off a cliff and Hope, Kristen, and Stefano thought he was killed. John's backpack was recovered, but the orchid was missing. Hope managed to find some of the orchid's seeds and Rolf made a cure using them. Later, John returned to the compound, but was poisoned by a native's dart. Dr. Rolf cured him as well and everyone left to go back to Salem. Later, Peter showed up at the compound with Jungle Madness. Dr. Rolf made Peter some pills, but Peter lost them when Peter attacked Rolf and took off in his plane. He joined in helping Stefano turn Hope into Gina, and when Stefano went to Salem, Rolf went with him.
Stefano hired Rolf's pregnant niece Marlo and convinced her to give her child to Lexie and Abe as their own. The reality was that Stefano had a deeper plan...he wanted Rolf to do a quick switch on Marlo and Hope's babies when they were born so that he could find out for certain whether or not Hope's child was also his. Marlo may have ruined the plan except that she fell down the stairs during an argument with Rolf, and broke her neck. Lexie, who saw the incident, was convinced to keep quiet. When Belle and Shawn discovered the body, Rolf (on Lexie's request) dissolved his niece's corpse in a vat of acid. At the same time, he was also helping Stefano transform waitress Hattie Adams into a Marlena look-alike. At Stefano's insistence, Rolf attempted to seduce Hattie, but Stefano's previous plan had worked too well...and Hattie's only allegiance was to Roman.
When Glen Reiber came to town, Stefano ordered Rolf to destroy any proof that he was the father of the baby Hope and Bo were raising. Unfortunately, Brandon had already performed the tests, and he and Lexie realized that Glen was J.T. Brady's father, meaning that she was raising Hope's child. Before anything could be done with this information, Rolf detonated explosives set up throughout Salem (the East Side Lab, the power plant, a lab near Tuscany, and the Salem Bridge). When Rolf planned to turn Hope back into Princess Gina, Lexie aided him in bringing her to the mansion. On Lexie's orders, Rolf mugged Barb and attempted to slit her throat, but amazingly, Barb lived. Rolf began activating the chip in Hope's brain, and at the mother of the year party, Hope briefly became Princess Gina and kissed John. Bo launching himself at the two of them was enough to keep Hope herself.
Rolf later became a Bioethics professor at the university so he could keep a close eye on the children of Salem, including Gemini twins Cassie and Rex. He even programmed the twins to kill anyone who came near the DiMeras. It was later revealed that Rolf was directly involved in the twins' conception and birth. When Rex realized that he wasn't Tony and Marlena's son after all but that Roman Brady was his father, he confronted Rolf. Before he could get the truth from him, Rolf died when a crate landed on him, and for awhile there, he was chauffeured around town in style, before his corpse was used to fake Larry Welch's death.