Question: What plot did Kurt Freiherr von Plettenberg and Claus von Stauffenberg work together on?

Context paragraphs:
Wessel Freytag von Loringhoven: Wessel Freytag von Loringhoven (10 November 1899 – 26 July 1944), was a colonel in the High Command of the German Armed Forces (OKW) and a member of the German Resistance ("Widerstand") against Adolf Hitler.  Loringhoven was a friend of Claus von Stauffenberg, who was the leader of the 20 July Plot to assassinate Hitler in 1944.

Adam von Trott zu Solz: Friedrich Adam von Trott zu Solz (9 August 1909 – 26 August 1944) was a German lawyer and diplomat who was involved in the conservative resistance to Nazism.  A declared opponent of the Nazi regime from the beginning, he actively participated in the Kreisau Circle of Helmuth James Graf von Moltke and Peter Yorck von Wartenburg.  Together with Claus von Stauffenberg he conspired in the 20 July plot, and was supposed to be appointed Secretary of State in the Foreign Office and lead negotiator with the western allies if they had succeeded.

Stauffenberg: The Schenk von Stauffenberg family is a noble (see Uradel) Roman Catholic family from Swabia in Germany, whose best-known member was Colonel Claus Schenk Graf von Stauffenberg – the key figure in the 1944 "20 July plot" to assassinate Adolf Hitler.

Livia von Plettenberg: Livia von Plettenberg (born (1988--) 14, 1988 ) is an Austrian female kickboxer and mixed martial artist, based in Portland, Oregon.  She competes professionally since 2005 and is currently in the Invicta Flyweight division.  Von Plettenberg's last MMA bout was at Invicta FC 6 against Kathina Catron which she won by unanimous decision.  According to the W.A.K.F ranking von Plettenberg was ranked fifth in the welterweight kickboxing division.

Hans-Ulrich von Oertzen: Born in Berlin to an aristocratic family, Oertzen followed his father into the army and trained as a general staff officer.  During the Second World War he was promoted to Major and by 1943 was serving in Army Group Centre under Generalmajor Henning von Tresckow, who was one of the leading members of the resistance.  He then helped Claus von Stauffenberg to develop Operation Valkyrie.  On 26 March 1944, he married Ingrid von Oertzen Langenn, and a selection of 240 letters he wrote to her from 1942 to 1944 were recently published in book form in Germany.

Alexander Schenk Graf von Stauffenberg: Alexander Franz Clemens Maria Schenk Graf von Stauffenberg (15 March 1905 in Stuttgart – 27 January 1964 in Munich) was a German aristocrat and historian.  His older twin brother Berthold Schenk Graf von Stauffenberg and youngest brother Claus Schenk Graf von Stauffenberg were among the leaders of the 20 July Plot against Hitler in 1944.

Karl von Plettenberg: Karl Freiherr von Plettenberg (18 December 1852 in Neuhaus – 10 February 1938 in Bückeburg) was a Prussian officer, and later General of Infantry during World War I.  He was Commandant-General of the Guards Corps, Adjutant General of the German Kaiser Wilhelm II and a recipient of Pour le Mérite.

Kurt von Plettenberg: Kurt Freiherr von Plettenberg (31 January 1891 in Bückeburg – 10 March 1945 in Berlin) was a German forester, cavalry officer and a member of the German Resistance (Widerstand).  He was involved in the preparations for the 20 July plot, an attempt to assassinate Adolf Hitler, Führer of the Third Reich.  Plettenberg belonged to the circle of close friends which included Claus Schenk Graf von Stauffenberg, Johannes Popitz, Ludwig Beck, Ulrich von Hassell, Carl-Hans Graf von Hardenberg and Fabian von Schlabrendorff.

Berthold Schenk Graf von Stauffenberg: Berthold Alfred Maria Schenk Graf von Stauffenberg (15 March 1905, Stuttgart – 10 August 1944, Berlin-Plötzensee) was a German aristocrat and lawyer who was a key conspirator in the plot to assassinate Adolf Hitler on 20 July 1944, alongside his younger brother, Colonel Claus Schenk Graf von Stauffenberg.  After the plot failed, Berthold was tried and executed by the Nazi regime.

20 July plot: On 20 July 1944, Claus von Stauffenberg and other conspirators attempted to assassinate Adolf Hitler, Führer of Nazi Germany, inside his Wolf's Lair field headquarters near Rastenburg, East Prussia.  The name Operation Valkyrie, originally referring to part of the conspiracy, has become associated with the entire event.  The apparent aim of the assassination attempt was to wrest political control of Germany and its armed forces from the Nazi Party (including the SS) and to make peace with the western Allies as soon as possible.  The underlying desire of many of the high-ranking Wehrmacht officers involved was apparently to show the world that not all Germans were like Hitler and the Nazi Party.  The details of the conspirators' peace initiatives remain unknown, but they likely would have included unrealistic demands for the confirmation of Germany's extensive annexations of European territory.

Supporting paragraphs: Kurt von Plettenberg 20 July plot
Answer: 20 July plot