A reconstitution arrangement for transferring the contents of a first container (136) with the contents of a second container (110) and subsequently retransferring the mixture to the first container (136), the arrangement including a transfer device (114) having a fluid passageway extending between first and second ends (111, 113), a cartridge holder (138) secured to second end (113) of the transfer device, the cartridge holder (138) having a needle (144, 145) with first and second piercing tips (117, 119), the first piercing tip (117) extending into the fluid passageway of the transfer device, a first container receiving portion (115) having the second piercing tip (119) extending therein and being arranged to receive the first container (136), a housing (118) secured to the cartridge holder with a plunger rod (122) within the housing, and a cover (130) extending over the transfer device (114), cartridge holder (138) and housing (118), the cover and transfer device having an interlocking arrangement to prevent removal of the cover (130) until activated by the second container (110).