Abstract: The internal tree cap of this invention has an isolation sleeve that stabs into a receptacle in the upper end of the tubing hanger. A seal on the exterior of the isolation sleeve seals an inner void within the isolation sleeve from an outer void. The inner void is the area between the tubing hanger wireline plug and the tree cap. The outer void is an area surrounding the tubing hanger above the tubing hanger upper seal and below the tree cap seal. The internal tree cap may have a bore and an upper crown plug that is wireline retrievable. Fluid will be trapped in the inner void when the isolation sleeve is stabbed into the receptacle above the tubing hanger. To allow displacement of the fluid when landing the upper crown plug, or when landing the upper crown plug and internal tree cap together, a vent passage leads through the tubing hanger to the outer void. This vent passage is preferably controlled by a metal sealing needle valve which is shut by an ROV or diver.