Contributed by David Verne
Early into Hadrian's reign, his Praetorian prefect, Attianus, claimed to have uncovered a conspiracy involving four Senators, all of them ex-consuls and included the high ranking general, Lusius Quietus There was no public trial and all four were hunted down and killed. It's not known exactly why these four were executed, but it is suspected they supported Trajan's expansionist policies and Hadrian wanted to get rid of them before they caused a ruckus over his abandonment of conquered Parthian territories.
The Senate was livid and quickly determined that they were dealing with a psychopathic maniac just as bad as Domitian. Hadrian went out of his way to claim that the murders were carried out by overzealous subordinates, and he had no knowledge of the plot. Hadrian assured them that their right to prosecute other Senators would be respected after this, but he had created a political bottomless pit. He would restore some good will with the Senate, but his relationship with them would be tenuous at best. He turned instead to the people and announced that he would cancel all outstanding debts on any state loan. Most people thought he was joking until the Praetorians burned the loan records in the Forum. With the people and the army behind him, he was relatively safe from the Senate. 
- Duncan, Mike (January 31, 2010). 82-Hadrian's Walls.