A conspiracy is "'an agreement between two or more persons by some concerted action to commit an offense.'" Ramsey v. Commonwealth, 2 Va. App. 265, 270, 343 S.E.2d 465, 469 (1986) (quoting Falden v. Commonwealth, 167 Va. 542, 544, 189 S.E. 326, 327 (1937)). "In Virginia, the crime of conspiracy is complete when the parties agree to commit an offense. No overt act in furtherance of the underlying crime is necessary." Gray v. Commonwealth, 260 Va. 675, 680, 537 S.E.2d 862, 865 (2000). "Liability as a conspirator is not dependent upon knowledge of the details and the scope of the conspiracy or the identity and role of each co-conspirator." Barber v. Commonwealth, 5 Va. App. 172, 179, 360 S.E.2d 888, 891 (1987).