Inclusion Criteria:

          -  Adults 18 years of age or older.

          -  Histopathologically confirmed melanoma with an injectable cutaneous or lymph node
             metastasis that has progressed in the opinion of the treating investigator despite
             administering a Food and Drug Administration (FDA) approved anti-PD1 agent, with or
             without ipilimumab.

          -  Eastern Cooperative Oncology Group (ECOG) performance status 0 to 1.

          -  Measurable disease according to RECIST 1.1.

          -  Acceptable coagulation status: international normalised ratio (INR) of blood clotting,
             prothrombin time and activated partial thromboplastin time within ≤1.5 x upper limit
             of normal (ULN).

          -  Completion of local therapy, such as radiation, surgical resection, injectable
             immunebased therapy, or topical pro-inflammatory agent, 21 days prior to first dose of
             protocol therapy.

          -  Adverse events from previous cancer therapies (excluding alopecia) must have recovered
             to grade 1 (CTCAE, most recent version). Stable grade 2 AEs such as endocrine
             conditions are allowed, and other chronic stable AEs may be considered on a case by
             case basis by the Principal Investigator.

          -  Clinical stability of brain metastases for at least 4 weeks prior to first day of
             study therapy.

          -  Acceptable liver and renal functions defined as:

               -  Total bilirubin ≤1.5 x ULN (does not include patients with Gilbert's Disease)

               -  Aspartate aminotransferase (AST, SGOT), alanine aminotransferase (ALT, SGPT) ≤3.0
                  x ULN

               -  Serum creatinine ≤1.5 x ULN

          -  Acceptable haematological function defined as (Patients can be transfused to meet the
             haemoglobin entry criteria):

               -  Haemoglobin ≥9 g/dL

               -  Neutrophils ≥1.5 x 10^9/L

               -  Platelet count ≥75 x 10^9/L

          -  Able to provide valid written informed consent.

          -  All women of childbearing potential must have a negative urine or serum pregnancy test
             at screening.

          -  All patients must agree to use barrier contraception (i.e. condom) during study
             treatment and for 2 months after the last virus treatment and 4 months after the last
             dose of chemotherapy and pembrolizumab.

        Exclusion Criteria:

          -  A concomitant medical condition requiring receipt of a therapeutic anticoagulant that
             in the opinion of the treating physician cannot safely allow for therapeutic injection
             of ONCOS-102 and tumor biopsies. Local clinical practice can be followed with regard
             to holding a therapeutic anticoagulant during invasive procedures such as biopsies.

          -  A concomitant medical condition that in the opinion of the treating physician would
             pose unreasonable additional risk to therapeutic injection of ONCOS-102.

          -  Receipt of Investigational agents within 28 days prior to first dose of protocol
             therapy.

          -  Any symptomatic autoimmune disease (such as lupus, scleroderma, Crohn's disease,
             ulcerative colitis) that requires administration of >10mg of prednisone equivalent.
             Lower dose steroids for conditions such as hypophysitis are allowed.

          -  Any prior severe adverse event attributed to prior anti-PD1 therapy that, in the
             Principal investigator's opinion, would contraindicate pembrolizumab administration
             such as:

               -  Grade 2 or higher pneumonitis

               -  Grade 4 AST or ALT elevation

               -  Grade 3 or higher colitis attributable to PD1 blockade; note that colitis
                  attributable to ipilimumab is not excluded

               -  Note: in the absence of clinical symptoms of pancreatitis, elevations of amylase
                  or lipase are not contraindications to therapy on this trial

          -  Known active infection with Hepatitis B Virus (HBV), Hepatitis C Virus (HCV), or HIV.
             Cleared HBV/HCV infection is not an exclusion, nor is HIV infection with cluster of
             differentiations 4 (CD4) counts >500 and an undetectable viral load.

          -  Active bacterial, viral, or fungal infections, requiring systemic therapy apart from
             anti-viral maintenance therapy for HIV.

          -  History of organ transplant.

          -  Patients requiring chronic systemic immunosuppressants, including steroids (prednisone
             daily equivalent of >10 mg).

          -  Brain metastases that are clinically unstable (e.g. showing unequivocal growth on
             imaging, requiring radiation therapy, or steroids >10mg of prednisone equivalent)
             within 4 weeks of first dose of study drug.

          -  Known severe congenital or acquired cellular or humoral immunodeficiency such as
             common variable immunodeficiency.

          -  Women who are pregnant or breast-feeding currently or are planning to conceive during
             or up to 4 months after end of protocol therapy.